UK Prime Minister Boris Johnson and President of the European Commission Ursula von der Leyen are to hold critical Brexit talks on Wednesday over future trade negotiations.
Mr Johnson and Ms von der Leyen are to talk in the evening ahead of an EU summit in Brussels on Thursday that the British premier had previously said needed to be decisive.
As the pressure builds on both sides to strike a deal, cracks have started to show between EU members, with German Chancellor Angela Merkel urging her partners to be realistic.
London and Brussels have sought to thrash out a deal on everything from trade to transport and energy co-operation.
However, the former EU member and the 27-nation bloc have clashed over the rules of fair competition, agreeing how these regulations will be policed, and securing access to UK waters for EU fishing fleets.
The EU has never recognised Mr Johnson’s self-imposed October 15 ultimatum, but diplomats have prepared a draft summit conclusion proposing to "intensify" the negotiations.
A source told reporters that Mr Johnson's call with Ms Von der Leyen would not necessarily prove decisive. The source said that London would not make any decision on next steps before hearing the result of Thursday's summit.
Ahead of the summit in Brussels, Ms Merkel has warned the EU that it must face reality, particularly on Britain’s position on fishing waters.
According to The Times British officials have blamed the deadlock on divisions within the EU and France's aggressive stance.
Ms Merkel said a deal was “particularly urgent from an Irish perspective.”
“We are going to continue to stand together in these withdrawal talks,” she said. “But we also have to take into account the reality: an agreement has to be in the interests of both parties, in British interests as well as the interests of the 27-member EU.”
Major differences between Berlin and Paris on how to deal with Brexit which had previously simmered beneath the surface, have come to the fore as the end of the Brexit transition looms.
Britain has also signalled it might show movement on the perennial issue of subsidy controls.
Britain left the bloc on January 31, but EU negotiator Michel Barnier and UK counterpart David Frost have been locked in inconclusive talks on a follow-on arrangement for cross-Channel business.
If no deal is reached, trade rules will revert to the bare bones of World Trade Organisation regulations.
On Tuesday, after meeting EU ministers in Luxembourg, Mr Barnier stressed that much remains to be done.
"The EU will continue to work for a fair deal in the coming days and weeks," he said.
In response, a UK government source accused Brussels of "using the old playbook in which they thought running down the clock would work against the UK".
Northern nations, in particular France, are holding a firm line on fishing, insisting that their boats operated in UK waters for centuries before the EU was formed.
