Unions must ensure there will be "sufficient" staffing during this week's ambulance strike to protect patients, the health secretary says.
Workers in England and Wales will walk out on Wednesday in a dispute over pay, but life-threatening emergencies will be responded to.
Unions say discussions were still taking place with ambulance trusts to draw up detailed plans for cover.
Steve Barclay said there is a lack of clarity about what is being offered.
He said it was for the unions to ensure they "meet their obligations" for emergency cover so that people in crisis get the care they need.
But Unite leader Sharon Graham, whose union is co-ordinating the ambulance strikes with Unison and GMB, said Mr Barclay will "have to carry the can if patients suffer".
"It's Steve Barclay who is holding the country to ransom," she told the Daily Mirror.
Unions say the government has the power to stop the ambulance strike - and action by nurses on Tuesday - if it signalled a willingness to discuss pay.
The ambulance walkouts will involve paramedics as well as control room staff and support workers.
The action by the three main ambulance unions - Unison, GMB and Unite - will affect non-life threatening calls, meaning those who suffer trips, falls or other injuries may not receive treatment.
Speaking to BBC Radio Four's Today programme, Welsh Ambulance Service CEO Jason Killings said about 15% of callouts were for issues which were immediately life threatening, although this varied across the regions.
He said a provision was in place for a "full return to duty, should there be a declared major incident", such as a terrorist attack.
Members of GMB are set to follow up the action with another walkout on 28 December.
The government's emergency Cobra committee will meet this morning to discuss how to lessen the impact of the ambulance strike. Ministers have already announced members of the military will be on standby to help out.
The unions representing NHS workers have asked for above-inflation pay rises for staff.
The governments in England and Wales have given staff an average rise of 4.75%, with a guaranteed minimum of £1,400.
Mr Barclay has said the government's pay award met the requirements of the recommendations of the independent NHS Pay Review Body and what was being asked for was "unaffordable".
While visiting an emergency call centre in Chelmsford on Sunday, Mr Barclay declined to be drawn on reports the government had ruled out a one-off payment for NHS workers to break the strikes deadlock, saying discussions between his department and the prime minister on the issue were private.
He added: "But I'm keen to continue a dialogue with the trade unions because there's a range of issues that matter to staff," he said, referring to issues such as technology and safety.
Both Unison and the Royal College of Nursing (RCN) union have threatened further strikes in the new year if an agreement is not reached.
Unison's health of health Sara Gorton urged Mr Barclay to "do the right" thing both for NHS workers and patients and "host genuine talks and put a better pay offer on the table".
"Ministers should take their heads out of the sand, stop pretending they can't boost wages and stop ignoring a worsening staffing crisis," she said.
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The UK has seen its last day of the cold snap, before temperatures soar to highs of 14C (57.2F) on Monday.
The freezing temperatures - which caused travel disruption and power cuts - is ending on Sunday evening.
Warnings for snow, ice and rain were in place for much of the country on Sunday - including an amber alert for ice in parts of northern England.
Temperatures are expected to jump by 15 degrees within 24 hours as a result of warmer air coming from the Atlantic.
BBC Weather said the bitterly cold, frosty weather was turning "to something much milder, wetter and windier".
Presenter Jennifer Bartram said: "The big swing in temperatures will be noticeable on Monday, and though it is unusual to see such a dramatic change, it's not unheard of.
"The change is all linked to where our air is coming from: we're replacing bitterly cold Arctic air with something much milder from the Atlantic," she added.
Between 2 and 3mm of ice on untreated surfaces was expected on Sunday as snow and ice continued across parts of the UK.
Presenter Ms Bartram said the rain on Sunday did signify milder weather, but "it will fall as sleet, snow or freezing rain" - especially across northern England.
Police forces across England have put out urgent pleas after receiving many calls about people on frozen water. Last week, four boys aged six, eight, 10 and 11 died after plunging into icy waters in Solihull.
Both night time and daytime temperatures are expected to increase over the next couple of days - with maximum daytime temperatures across the UK ranging from 11C to 14C, according to the Met Office's Marco Petagna.
Mr Petagna said temperatures in the low teens were not uncommon at this time of year, but the contrast of conditions going from very cold to very mild in a day or two is quite unusual.
He said a leap of "15 degrees or more" was expected in some snow-covered areas on Monday, he said.
There are fiveflood warnings in place for south-west England, including in south Devon, from late Sunday through to Monday. This warning means flooding is expected.
There have also been 34 flood alerts issued across the country.
Peter Jenkins from Water UK said the recent freezing weather had been "disruptive" and urged people to check their water pipes are well insulated.
"The last thing we want is for people to experience further disruption as temperatures rise this weekend, putting many homes at risk of burst pipes due to freeze-thaw."
This weekend as the weather warms, check your pipes are well insulated to avoid damage from freeze-thaw. Frozen pipes can burst as they thaw, causing damage and leaks. Look out for pipes in lofts and outdoor taps. Find out more: https://t.co/5UewFb6aoh#watersworthsavingpic.twitter.com/zlHJZB4SgC
Snow and ice across Scotland and northern England until 21:00
Heavy and persistent rain across the south west of England and southern Wales from 18:00 until 06:00 on Tuesday
An amber warning for ice was also in place for north east and north west England, East Midlands, West Midlands and Yorkshire and Humber until 20:00.
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In the last week, the country has been experiencing a severe cold snap with overnight temperatures dropping to lows of -10C to -15C.
Braemar in Scotland dropped to as low as -17.3C on Tuesday - the coldest temperature since February 2021.
The UK Health Security Agency had earlier issued a level three cold weather alert for all of England until midnight on Sunday which it warned could "increase the health risks to vulnerable patients and disrupt the delivery of services".
The severe conditions in recent days has led to serious damage and disruption.
In Shetland, the 5,289 homes that lost power at the start of the week have now had their supplies restored. A major incident was declared on Tuesday after snowstorms brought down power lines.
Find out the weather forecast for your area, with an hourly breakdown and a 14-day lookahead, by downloading the BBC Weather app: Apple - Android - Amazon
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Britain is bracing for one of the most disruptive weeks of strike action in recent history after the government signalled its determination to face down the unions despite calls for pay negotiations from health leaders and some Conservative MPs.
Nurses, ambulance workers, customs and immigration staff, postal and rail workers will all walk out in the coming days.
Prime minister Rishi Sunak faces a mounting challenge in dealing with the strikes. Some Tory MPs have urged the government to reopen talks on nurses’ pay after health leaders warned that ongoing disruption within the NHS could jeopardise public safety.
Nurses’ union leaders have raised the pressure on Downing Street by threatening further walkouts next year.
Pat Cullen, general secretary of the Royal College of Nursing, said ministers would have a 48-hour window after Tuesday’s strikes to engage with pay talks, after which the union would announce more widespread strike action in the new year.
Matthew Taylor, chief executive of the NHS Confederation, urged trade unions and the government to “try to find a way through”, warning that this week’s strikes pose a risk to patient safety.
Health secretary Steve Barclay is expected to write to the RCN ahead of Tuesday’s industrial action. However, there was no sign of his having shifted position and officials close to him dismissed reports that the government was considering offering a one-off lump sum to nurses.
Cabinet minister Oliver Dowden said on Sunday that the government’s door was always “open to engagement with the unions”. But he stood by the decision by ministers to stick with recommendations in July from the Independent NHS Pay Review Body for a £1,400 increase for most NHS staff.
“We will be resolute in response to this, because it would be irresponsible to allow public sector pay and inflation to get out of control,” Dowden told the BBC.
Sunak is facing growing unease within his parliamentary party over his handling of the industrial disputes.
Caroline Nokes on Sunday became the latest Tory to urge ministers to “get back round the table” with the RCN. “There is a real merit in having another look at negotiations and seeing where they get to,” she told the BBC.
This sentiment has been echoed by senior Conservatives such as former justice minister Robert Buckland, former Tory party chair Jake Berry and chair of the health and social care select committee Steve Brine.
Some Tory MPs are nervous about how the disruption is playing out among the public. “There is more sympathy for nurses and ambulance workers — which is inevitably tricky for Rishi,” a senior Tory said.
A survey by Opinium found that around 50 per cent of those polled supported the government negotiating on pay, even if the consequence meant offering higher pay packages than recommended by the independent body.
“The question is the public resolve and whether people get fed up with striking workers and start to question the government’s strategy or that of the unions,” another Conservative parliamentarian said.
Some MPs — even those backing Sunak’s approach — believe the government will be forced to relent on some issues eventually given the multitude of strikes.
“In practical terms the government needs to be seen to have won at least one industrial dispute,” one former minister said. “If they are seen to be hardline in one area such as rail unions they can then be flexible on another such as health.”
A man, aged 40, and a woman, aged 41, were arrested on 9 December on suspicion of causing or allowing the death of a child and a separate case of wilful neglect.
Both have been charged with neglect.
They have been remanded in custody.
Post-mortem tests on the body are due to be held, the police force said.
The force said the home's current occupiers were not connected to the inquiry.
A woman has died after being injured in a crush at a gig at London's Brixton O2 Academy that left several others hurt.
The concert, by Afro-pop singer Asake, had to be abandoned part-way through after a "large number of people" tried to force their way inside on Thursday, the Met Police said.
Rebecca Ikumelo, 33, from Newham, east London, died in hospital on Saturday morning, the Met said.
Two other women aged 21 and 23 remain in a critical condition, police added.
Asake said he was "overwhelmed with grief" and "devastated" by her death.
The artist said he had spoken with Ms Ikumelo's family and asked people to "keep them in our prayers".
Academy Music Group, which owns and runs the venue, said in a statement: "All at O2 Academy Brixton and Academy Music Group are deeply saddened by the news of the tragic death of Rebecca Ikumelo.
"We send our heartfelt condolences to Rebecca's family and friends, and our thoughts are with everyone affected by this devastating news at this extremely difficult time."
He said it was "vital that the investigation into what happened concludes as soon as possible" and added that City Hall was working with authorities "to ensure nothing like this happens again".
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Videos on social media showed the crowd stretching from the road outside to the venue's doors.
Speaking at the scene on Friday, Ch Supt Colin Wingrove said: "I'd like to extend my sympathies to all those who have been affected.
"Having seen some of the really upsetting images on social media our thoughts are with them," he added.
The force said more than 4,000 people were in attendance at the gig and it has set up a website for people to submit relevant photos and videos.
In a statement outside Brixton police station on Friday afternoon, Mr Wingrove said officers were called by staff at the venue "following reports that a large number of people were attempting to force entry".
He added: "Some officers provided first aid and CPR to members of the public in order to save life."
Florence Eshalomi, Labour MP for Vauxhall whose constituency includes Brixton, tweeted on Saturday: "I visited the site this morning and I've been dreading this news ever since the incident and hoping it would never never come.
"My thoughts and prayers to Rebecca Ikumelo's family and friends. Such a tragic loss of a young 33yr with so much life ahead of her."
The first officers were reported to be on the scene at 21:11 GMT, seven minutes after they were called.
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The concert was the final performance of three sold-out shows at the venue by Nigerian singer Asake, sometimes known as Mr Money.
Before the gig, he had posted on Twitter asking fans not to try to gain entry unless they had tickets.
In a statement published on Twitter on Saturday, Asake said: "I am overwhelmed with grief and could never have imagined anything like this happening.
"My team and I are still awaiting the full debrief back from the venue management and the police to determine what exactly led to all the disruption caused and ultimately to Rebecca's passing."
He urged anyone with information to contact police.
Thames Water has apologised for "the flooding and distress" caused by a burst pipe in north London that forced several homes to be evacuated.
A 42-inch water main burst overnight and unleashed half a metre of flooding across an area of around 800 metres, London Fire Brigade (LFB) said.
Eight fire engines and around 60 firefighters were called to Belsize Road in Camden at around 3am on Saturday morning.
The fire brigade said several homes were flooded and firefighters had to lead around 20 residents to safety.
Footage shared on social media shows emergency services using small boats and helping residents wrapped in blankets to safety.
Image:(L to R) Emma Thompson, Nick Carragher and Sophie Adams return to the flat they share
Sophie Adams, who lives near the flood, woke to find only a drizzle of water when she turned on the tap to make a cup of tea.
"Now there's nothing come out of the taps at all. They're bone dry," she said.
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Ms Thompson added: "We are moaning about having no water but there are people whose flats are flooded."
Police officers were telling people in the area that they may not have water for a couple of days.
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One firefighter spoke of basement windows being forced inwards by the power of the gushing water.
In a statement, Thames Water apologised for the lack of water and the disruption.
"We're really sorry for the flooding and distress this has caused, as well as the impact on local water supplies," it said.
On Saturday its engineers managed to turn off the flow from a large burst pipe in Loudoun Road, which took some time as some valves were under parked cars.
Thames Water did not yet know how long it would take to refill the network, but said heating should still work in the meantime.
