Prime Minister Boris Johnson is set to announce a second national lockdown for England as the UK passed one million Covid-19 cases.
Non-essential shops and hospitality will have to close for a month, sources told the BBC.
But unlike the restriction in the spring, schools and colleges are to be allowed to stay open.
It comes as documents suggested the UK was on course for a much higher death toll than during the first wave.
The lockdown is also expected to include restrictions on travel and is due to come into force on Thursday, lasting until 2 December, BBC political correspondent Nick Eardley said.
The prime minister is due to lead a news conference later, after holding a cabinet meeting to discuss the coronavirus response.
He is set to be joined by England’s chief medical officer Chris Whitty and the government’s chief scientific adviser Sir Patrick Vallance for the briefing.
The UK recorded another 21,915 confirmed coronavirus cases on Saturday, bringing the total since the pandemic began to 1,011,660.
Another 326 people were reported to have died within 28 days of a positive test.
The UK is the ninth country to reach the milestone of a million cases – after the US, India, Brazil, Russia, France, Spain, Argentina and Colombia.
But the true number of infections is expected to be higher due to a lack of widespread testing at the start of the pandemic.
Elsewhere in the UK, Wales’ First Minister Mark Drakeford said the 17-day “firebreak” there will end as planned on 9 November.
He said that his cabinet will meet on Sunday to “discuss any potential border issues for Wales in light of any announcement by No 10”.
Scotland’s First Minister Nicola Sturgeon has issued new advice that people should not travel to or from England, except for essential purposes, ahead of the nation’s five-level system of restrictions coming into force on Monday.
Documents seen by the BBC, understood to be part of a presentation by the government’s pandemic modelling group SPI-M shown to Mr Johnson, show projections by several different groups of the likely course of the disease.
All models predict that hospitalisations are likely to peak in mid-December, with deaths rising until at least late December before falling from early January.
A separate document circulating in government – based on NHS England modelling from 28 October – warns that the NHS would be unable to accept any more patients by Christmas, even if the Nightingale hospitals are used and non-urgent procedures cancelled.
It warns that south-west England and the Midlands will be the first to run out of capacity, potentially within a fortnight.
These latest papers come after a statement from the Scientific Advisory Group for Emergencies (Sage) revealed that Covid is spreading much faster in England than the predicted “worst-case” scenario.