British Prime Minister Boris Johnson and EU chief Ursula von der Leyen hold crunch talks on Wednesday with time running short for the two leaders to decide on whether it is worth pursuing post-Brexit trade negotiations.
The call between the two comes on the eve of an EU summit that Johnson had declared to be the deadline for a breakthrough, but a source close to the talks said he would only decide after the meeting.
The European Union had never recognised the October 15 ultimatum, but diplomats have prepared a draft summit conclusion proposing to "intensify" the negotiations.
A source close to the negotiations told reporters that Johnson's call with Von der Leyen would not necessarily be decisive. The source said that London would not make any decision on next steps before hearing the result of Thursday's summit.
EU spokesman Eric Mamer said the call would take place at 8:30pm (1830 GMT) and would also involve EU Council president Charles Michel.
On Thursday, the 27 EU leaders will meet in Brussels and the log-jam in the post-Brexit trade talks with their former partner will be the first item on their summit programme.
According to draft conclusions seen by AFP, they will express concern "that progress on key issues of interest to the Union is still not sufficient for an agreement to be reached."
And they will invite EU negotiator Michel Barnier to "intensify negotiations" to strike and implement a trade deal before January 1, when the UK will have left the single market.
Britain left the European Union on January 31, but Barnier and UK negotiator 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.
- Fair competition -
Both sides insist they are ready for this -- and would prefer it to accepting a deal that breaks their red lines -- but experts forecast severe economic disruption.
Seeking to spur progress, Johnson declared October 15 to be his deadline to reach a deal or walk away. This date now seems likely to pass without talks breaking down.
On Tuesday, after meeting EU ministers in Luxembourg, 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 tweeted.
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."
Europe's three main concerns are agreeing on the rules of fair competition, agreeing how these rules will be policed and securing access to UK waters for EU fishing fleets.
Britain wants to reassert sovereignty over its waters and refuse EU legal oversight over the deal -- insisting it wants a simple trade deal of the kind the EU signed with Canada.
Brussels in turn stresses that Britain's economy is far more integrated with and closer to the EU's than Canada, and that the single market must be protected from British backsliding.
Northern fishing 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.
French Foreign Minister Jean-Yves le Drian said: "As things currently stand, the hypothesis of a 'no deal' is a very real one, and also one that is unfortunately very likely today."
On Tuesday, Irish Foreign Minister Simon Coveney said the two sides were still "very far apart" and insisted EU trawlermen would not be hung out to dry.
- ' Face reality' -
In a speech to the EU Committee of the Regions on Tuesday, Germany's Chancellor Angela Merkel said "we will not leave Ireland alone here", pledging EU unity.
"We will discuss this intensively at the European Council in two days' time, we want an agreement," she said.
"But we must also face up to reality, because an agreement must of course be in the interests of both sides."