And fresh restrictions to limit the spread of the Omicron variant are "inevitable" in London, mayor Sadiq Khan said.
It comes as Deputy First Minister John Swinney said the Scottish Government will update parliament next week on whether new restrictions are needed in Scotland to curb the “really aggressive” spread of the new variant.
Sadiq Khan declared a major incident in London on Saturday over the rapid rise in cases.
It is “inevitable” that new measures will be brought in, he told the Andrew Marr show on Sunday.
"The direction of travel is only going one way: cases doubling over two days”, he said.
Mr Khan said: “I think if we don’t bring in new restrictions sooner rather than later, you’re going to see even more positive cases and potentially public services like the NHS on the verge of collapse, if not collapsing.”
He added: “I think we should be able to celebrate Christmas safely. But I think sooner rather than later we’re going to look at social distancing, we’re going to have to look at household mixing.
“Because if we don’t, the number of cases is only going one way and the issue isn’t the seriousness of the consequences, not just that, it’s also the numbers of people who have the virus.”
Mr Javid said advice from UK Government scientific advisers warning of the possible impact on hospital admissions from Omicron is “sobering” and said there are “no guarantees” when asked about the possibility of further restrictions.
He told The Andrew Marr Show: “It’s a very sobering analysis. We take it very seriously.”
He added: “We do have to challenge data and underlying assumptions, I think that is appropriate, and take into account a broader set of facts.”
When it was suggested to him he was not ruling out a circuit-breaker or new restrictions before Christmas, Mr Javid said: “There are no guarantees in this pandemic, I don’t think.
“At this point we just have to keep everything under review.”