Every Briton over the age of 70 will be told "within the coming weeks" to stay at home for an extended period to protect themselves from coronavirus.
When it happens, they will be asked to stay home for "a very long time", Health Secretary Matt Hancock said.
The government is to release social distancing advice for elderly people on Monday - but they will not yet be asked to self-isolate for long periods.
Fourteen more people have died from the virus, bringing deaths in the UK to 35.
Mr Hancock told the BBC that manufacturers were being asked to help produce medical equipment, such as ventilators, to help with an expected surge in demand by the NHS.
He also said hotels could be converted into makeshift hospitals, while the government has begun negotiating with private healthcare providers to obtain thousands of extra beds in private hospitals.
What are the latest figures?
The number of confirmed UK cases of the virus has reached 1,372, with 40,279 people tested, according to the latest Department of Health figures.
Most of the 35 coronavirus-related deaths in the UK have so far been people aged over 60 and with underlying health conditions.
People self-isolating with mild symptoms of the virus are no longer being tested. The government says tests will primarily be given:
- To all patients needing hospital treatment for pneumonia, acute respiratory distress syndrome (ARDS) or a flu-like illness
- Where an outbreak has occurred in a residential or care setting, for example long-term care facilities or prisons
What are the government's plans?
Mr Hancock said the over-70s and people with certain health conditions would soon be asked to self-isolate - but he did not say for how long.
He told the BBC's Andrew Marr Show people without symptoms would still be able to visit older relatives and friends as long as they stayed 2m (6ft) away from them.
The health secretary also said the NHS would stop non-urgent surgery and retrain medics from other specialisms to treat those with the disease caused by coronavirus, Covid-19.
He said details of emergency legislation giving the government more powers to deal with the outbreak will be shared on Tuesday.
The health minister for Wales, Vaughan Gething, said it was "entirely possible" elderly people would be asked to self-isolate for long periods.
"That shouldn't be a surprise," he added.
But the Scottish government said it had no plans to isolate the elderly, and would instead "ask them to reduce social contact".
Jeane Freeman, Mr Hancock's counterpart in Scotland, said: "We don't want people who are elderly to be stuck in their homes alone not contacting anyone, with their families not able to be in touch with them and to help them."
Scottish ministers have also advised against gatherings of 500 people or more. They do not have the power to call off events but have urged organisers to "act responsibly" by cancelling such gatherings from Monday.
Who are the latest victims?
The 14 patients whose deaths were announced on Sunday were aged between 59 and 94 and all had underlying health conditions, NHS England said.
Among them was retired police officer Nick Matthews, 59, of Nailsea, near Bristol, who died at Bristol Royal Infirmary in the early hours of Saturday.
His wife, Mary, paid tribute on Facebook, saying she had lost her "soul mate" and "best friend".
She urged people not to visit her and her family until their own test results for the virus came back.
Mr and Mrs Matthews had returned from a holiday in Fuerteventura, in the Canary Islands, on 29 February.
How many ventilators are needed?
Mr Hancock said there were 5,000 ventilators available at the moment - but that many times that number would be needed.
Car companies and weapon manufacturers are among the firms the government has asked to help to make ventilators to treat Covid-19 patients.
Ventilators treat severe breathing problems caused by Covid-19 by giving people oxygen and removing carbon dioxide from their lungs.
Digger manufacturer JCB said Prime Minister Boris Johnson had asked if it could help.
JCB chairman Lord Bamford said it was "unclear" whether the firm could agree to do so, but that engineers were "actively looking" at the request.
Why and when should vulnerable people self-isolate?
Shielding the vulnerable and elderly will be an essential part of the government's strategy when cases are rising rapidly - it was one of the decisions signed off at an emergency Cobra meeting on Thursday.
Half of the overall cases are expected within a period of a few weeks, with 95% in a period of around 10 weeks.
So officials will ask those at most risk of developing severe illness to stay at home.
They believe if they get the timing right and people adhere to it the move could reduce the number of deaths by up to a third.
But it of course carries its own risks - mentally and physically.
They believe the longest they could ask people to do this for is around 12 weeks.
That's why it's essential people don't start too soon. At the moment the vulnerable groups should be protected to a degree by the fact that the small number of people with the virus should be self-isolating.
But officials recognise individuals will make their own decisions about when to start.
What else is going on?
- South Africa has barred some foreigners from entering and will close schools
- EU states including Germany, Austria and France are among the latest to announce radical action to curb the spread of the virus
- The Foreign Office advised against all but essential travel to Spain after the government there announced emergency restrictions
- The Foreign Office has issued the same advice for the US, effective from Tuesday morning, after President Trump decided to extend a European travel ban to include the UK
- Airlines warned the UK's aviation industry may not survive the pandemic without emergency financial support
- And about 600 Britons are among passengers stranded on a Fred Olsen cruise ship in the Bahamas after five people on board tested positive for the virus. The company said all onboard bars and restaurants are still open and passengers had been given a "complementary all-inclusive drinks package"
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