A tougher three-tiered system of local restrictions will come into force in England when the lockdown ends on 2 December, Downing Street has said.
Boris Johnson is expected to set out his plan - including details of how families can see different households at Christmas - to MPs on Monday.
More areas are set to be placed into the higher tiers to keep the virus under control, No 10 said.
And some tiers will be strengthened to safeguard lockdown progress.
It is not yet clear exactly how restrictions could change - but it is understood the 10pm curfew on pubs and restaurants will be extended.
Mr Johnson is expected to say that, while last orders must be called at 10pm, people will get an extra hour to finish their food and drinks.
Full details of the so-called "Covid winter plan" are expected on Monday, after cabinet discussions on Sunday.
A No 10 spokeswoman said: "Everyone's efforts during the current national restrictions have helped bring the virus back under control, slowed its spread and eased pressures on the NHS.
"But the prime minister and his scientific advisers are clear the virus is still present - and without regional restrictions it could quickly run out of control again before vaccines and mass testing have had an effect.
"That would put in jeopardy the progress the country has made, and once again risk intolerable pressure on the NHS."
Some local measures will be the same as those in the previous three tier system, used in England to tackle the spread of coronavirus up until the current lockdown began.
But the government's Scientific Advisory Group for Emergencies (Sage) is expected to publish papers on Monday saying that measures in the previous tiers were not strong enough.
The prime minister will acknowledge that the measures are difficult, while making clear they are not to last longer than is absolutely necessary, and that the need to support the economy is being taken into account.
2px presentational grey line
English tier system - at a glance
Pre-lockdown, there were three tiers of restrictions - medium, high, and very high:
Medium / Tier 1: Rule of six if meeting indoors or outdoors; pubs and restaurants shut at 10pm
High / Tier 2: No household mixing indoors; rule of six applies outdoors; pubs and restaurants shut at 10pm
Very high / Tier 3: No household mixing indoors or in some outdoor spaces; pubs and bars not serving meals are closed
2px presentational grey line
It comes after newspaper reports suggested families could be allowed to meet for up to a week over Christmas as part of a UK-wide relaxation of coronavirus rules.
According to the Daily Telegraph, several families could be allowed to join in one "bubble" and mix between 22 and 28 December.
The plan will include guidance on how people will be able to celebrate Christmas, but ministers have made clear the festive season will be different to normal - with some restrictions expected to remain in place. The government will identify the tiers that each area will be placed into on Thursday.
MPs are expected to be given a vote to approve the new system in the days before it comes into force.
Earlier this month, Mr Johnson promised MPs would have a say on any restrictions imposed after the current lockdown ended.
Many of his own MPs are opposed to stricter measures - around 50 have joined the recently-formed Covid Recovery Group (CRG),
Led by former chief whip Mark Harper and ex-Brexit minister Steve Baker, the group has warned they cannot support a tiered approach unless the government produces evidence to show measures "will save more lives than they cost".
What are the current rules where you live?
England tiers may need strengthening - adviser
Ministers want 'greater consistency' in tier system
During a vote on the current lockdown earlier this month, 32 Conservatives rebelled to oppose the measures and 17 more, including former Prime Minister Theresa May, abstained.
In a letter to the prime minister on Saturday, the group warned against inflicting "huge health and economic costs". Sources close to the group said it had been signed by 70 Conservative MPs, although the group's leaders were the only signatories identified.
The letter continued: "We cannot live under such a series of damaging lockdowns and apparently arbitrary restrictions, and expect our constituents to be grateful for being let out to enjoy the festive season, only to have strict restrictions imposed on them afterwards that cause them health problems and destroy their livelihood."
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Labour has so far been supportive of the need for restrictions to slow the spread of Covid-19, making a full-scale Commons defeat on the plan unlikely.
But the opposition party has been urging the government to lay out its plan for what will happen when the national restrictions end.
Labour's shadow chancellor Anneliese Dodds, in a speech on Saturday, said the nation could not be allowed to return "to the shambles we had before this lockdown".
She called for clarity about what economic support package would accompany different types of restrictions.
Under England's previous three-tiered system, regions were classified as either tier one - "medium", tier two - "high" or tier three - "very high", and each one had different lockdown rules.
There are also different rules in Wales, Scotland and Northern Ireland.
On Saturday, the UK recorded another 19,875 new coronavirus cases and 341 deaths within 28 days of a positive test.
The number of deaths was down from 511 on Friday, and 462 on Saturday 14 November.
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