Boris Johnson has spent a second night in intensive care as he continues to receive treatment for coronavirus.
Mr. Johnson is being kept in St Thomas’ Hospital in London “for close monitoring”, Downing Street said.
The PM is “comfortable, he’s stable, he’s in good spirits”, said health minister Edward Argar on Wednesday.
No 10 also suggested the three-week review into whether the coronavirus lockdown could be eased would not go ahead as planned on Monday.
Asked on when the measures might be lifted, Mr. Argar said the scientific evidence “isn’t yet there to allow us to make us a decision”.
“We have to be over that peak before we can think about making changes,” he said, adding: “It’s too early to say when we will reach that peak.”
Foreign Secretary Dominic Raab, who is deputizing for the PM, said on Tuesday he was “confident” the PM would recover from this illness, describing him as a “fighter”.
Speaking at the Downing Street coronavirus briefing, he said Mr. Johnson was receiving standard oxygen treatment and was breathing without any assistance, such as mechanical ventilation or non-invasive respiratory support.
The prime minister was admitted to St Thomas’ on Sunday, on the advice of his doctor, after continuing to display symptoms of a cough and high temperature 10 days after testing positive for the virus.
The Queen and other senior royals sent messages to Mr. Johnson’s family and his pregnant fiancee, Carrie Symonds, saying they were thinking of them and wished the PM a full and speedy recovery.
Latest on lockdown
A ban on public gatherings of more than two people and the closure of shops selling non-essential goods were among the series of restrictions announced by Mr. Johnson on 23 March to tackle the spread of coronavirus.
He had said a relaxation of the rules would be considered in three weeks, which would be 13 April.
But on Tuesday, Downing Street suggested that the review would not go ahead on the scheduled date and would instead take place after the three-week mark.
Ahead of a spell of the sunny weather forecast in some parts of the UK later this week, Mr. Argar urged people to stay at home “however lovely the weather this Easter weekend”.
“If we are, as the statistics appear to show, making a little bit of progress, now’s the time to hold to it,” he said.
According to the government’s coronavirus legislation, the health secretary must review the need for restrictions at least once every 21 days, with the first review to be carried out by 16 April.
Mayor of London Sadiq Khan said: “I think we’re nowhere near lifting the lockdown.
“We think the peak – which is the worst part of the virus – is still probably a week and a half away.”
Also at Tuesday’s briefing, Mr. Raab was also asked about whether his role deputizing for Mr. Johnson gave him full prime ministerial responsibility.
The foreign secretary said he was standing in for the prime minister “whenever necessary” – including leading the daily meetings of the coronavirus “war cabinet”.
Mr. Raab said decisions would be made by “collective cabinet responsibility – so that is the same as before”.
“But we’ve got very clear directions, very clear instructions from the prime minister, and we’re focused with total unity and total resolve on implementing them so that when he’s back, I hope in very short order, we will have made the progress that he would expect and that the country would expect,” Mr. Raab added.
Meanwhile, the first patients have been admitted to the NHS Nightingale Hospital in east London – a temporary facility set up at the ExCel conference center.
The admissions come two weeks after the hospital with a planned capacity of 4,000 was formally announced – although an NHS spokesperson stressed limits had not been reached at other sites in London.
It came as the number of coronavirus hospital deaths in the UK rose to 6,159 on Tuesday – a record increase of 786 in a day, the Department of Health and Social Care said, compared with 439 on Monday.
However, the government’s chief scientific adviser told the Downing Street briefing the number of coronavirus cases in the UK “could be moving in the right direction”.
Sir Patrick Vallance said it was “possible that we’re beginning to see… the curve flattening”.
As of 09:00 BST on Tuesday, 213,181 people have been tested, of which 55,242 tested positive, the Department of Health and Social Care said.
Overall, 266,694 tests have been concluded, with 14,006 tests carried out on Monday.