The EU’s chief negotiator Michel Barnier has delayed his return to Brussels and is expected to remain in the UK until Wednesday to carry on intensive discussions with his British counterpart Lord David Frost.
Barnier originally arrived in London on Thursday to resume the stalled negotiations and had been expected to return on Sunday ahead of the talks switching this week to the Belgian capital.
The decision to stay in London was thought, at least in part, to be related to soaring coronavirus infection rates in Brussels.
The prime minister’s official spokesman said: “We are in now what is an intensive phase of negotiations.
“I wouldn’t wish to pre-empt what’s being discussed.
“It’s the first time that we have been negotiating on legal texts and across all areas at the same time and we have welcomed that fact.
“But there is also much work to be done if we are going to bridge what are the significant gaps that remain between our positions in the most difficult areas and time is very short.”
Meanwhile Boris Johnson played down speculation that he was delaying the outcome of negotiations with Brussels until after the US election.
Talks on a UK trade deal with the US have begun under Donald Trump, but his rival for the White House Joe Biden may not share the Brexit-supporting president’s enthusiasm.
But the prime minister said: “The two things are entirely separate.
“On EU negotiations … they’ve come back, I’m very glad to say, to discuss the way forward, we’ll see where we go.”
On the US election, Johnson said any UK prime minister would say they “don’t believe in getting involved” in the process.
Time is running short if there is to be a UK-EU agreement before the Brexit transition period comes to a close at the end of the year.
The UK and the EU had previously said they would need to get a deal by mid-October if it was to be implemented in time, but reports from Brussels have suggested mid-November might be the latest an agreement could be reached.
The main obstacles to a deal remain fishing rights, so-called “level playing field” rules to ensure fair competition and governance arrangements for any agreement.