EU ministers meeting in Luxembourg are to receive an update on Brexit talks from the bloc’s chief negotiator, Michel Barnier, later.
Discussions between EU and UK officials aimed at reaching a Brexit deal have intensified in recent days.
Hopes of a deal being agreed before the 31 October Brexit deadline were boosted after a meeting between Boris Johnson and his Irish counterpart last week.
But Mr Barnier this week said “big gaps” remained between the UK and EU.
Finland’s prime minister, Antti Rinne, who holds the EU’s rotating presidency, went further, saying there was not enough time for a deal to be reached.
After meeting the European Council’s president-elect Charles Michel, Mr Rinne said: “I think there is no time in a practical or legal way to find an agreement before the EU Council meeting. We need more time.”
In response, housing secretary Robert Jenrick rejected the remarks, stressing a “great deal” of progress had been made and negotiators are working “very intensively”.
He told BBC’s Newsnight: “The EU is capable of moving extremely quickly if they wish to.
“Like any negotiation with the EU, and in fact with any major negotiation in life, everything happens at the last minute.
“This was always going to be both complicated and come down to the final hours and days, so this doesn’t surprise me. We are going to work round the clock to try to secure it.”
The comments came as negotiators stepped up efforts to work out a way to break the deadlock over the Irish backstop, the contingency measure to prevent a hard border on the island of Ireland that is seen as the key factor in the talks.
On Monday, Irish deputy premier Simon Coveney raised hopes on an agreement being reached before the EU summit by saying a deal could possibly be achieved as soon as this week.
“But we’re not there yet,” he added.
In similar comments, Mr Johnson told senior ministers there was “still a significant amount of work to get there” but a “pathway” to a deal was still visible.
With talks in Brussels ongoing, a Cabinet meeting expected to take place on Tuesday has been postponed and is now likely to take place on Wednesday. Downing Street sources say it is to allow for a fuller update on Brexit.
It’s extremely hard to see how a new Brexit deal can still be agreed by this Thursday.
Negotiations continue – but time is tight, and, to use the words of even the most upbeat of those involved, “there’s still much work to do”.
EU internal talk is focusing now on a possible “holding pattern statement” at this week’s EU leaders summit, along the lines of “we’ve made great progress in negotiations but still need more time”.
There are also renewed mutterings about a new Brexit summit, maybe towards the end of the month.
The two-day EU summit is crucial because the prime minister must get a new deal approved by MPs by Saturday if he is to avoid asking for a Brexit delay.
The Benn Act passed by MPs opposed to no-deal says he must ask for an extension to the Brexit deadline if MPs do not back a deal by then.
However, Mr Johnson has repeatedly ruled out requesting such an extension, prompting speculation that he may seek to sidestep the legislation.
Leader of the Commons Jacob Rees-Mogg suggested it could be possible for the government to use European law to achieve no-deal.
“Theresa May got an extension not through UK law but through EU law and, until the 1972 European Communities Act is repealed, EU law is superior law in the UK,” he said on BBC Radio 4’s Westminster Hour.
Labour has threatened court action to force the PM to obey the legislation.
Regardless of what happens in Brussels, a showdown is anticipated in an emergency sitting of Parliament on Saturday – the first in 37 years.
MPs will be able to back or reject any deal presented to them, or there will be discussions on what to do next.
Timeline: What’s happening ahead of Brexit deadline?
Thursday 17 October – Crucial two-day summit of EU leaders begins in Brussels. This is the last such meeting currently scheduled before the Brexit deadline.
Saturday 19 October – Special sitting of Parliament and the date by which the PM must ask the EU for another delay to Brexit under the Benn Act, if no Brexit deal has been approved by MPs and they have not agreed to the UK leaving with no-deal.
Thursday 31 October – Date by which the UK is currently due to leave the EU.