EU's Michel Barnier warns 'just a few hours' left to strike Brexit trade deal

EU chief negotiator Michel Barnier has warned there are "just a few hours" left to strike a post-Brexit trade deal with the UK, as the two sides stand at the "moment of truth".

As talks resumed on Friday, Mr Barnier said there was a chance of getting a deal in time for the end of the transition period on December 31, but said the path to a breakthrough was "very narrow".

His warning came after Boris Johnson told European Commission president Ursula von der Leyen the EU must "significantly" shift its stance on fishing, for an agreement, as the brinkmanship continued.

The EU set the latest deadline that an agreement must be ready by Sunday night to have enough time for MEPs to ratify it, while the House of Commons has been warned it may need to to hastily return from Christmas recess to vote on a deal.

"It's the moment of truth," Mr Barnier told the European Parliament in Brussels.

"We have very little time remaining, just a few hours, to work through these negotiations in useful fashion if we want this agreement to enter into force on January 1.

"There is a chance of getting an agreement, but the path to such an agreement is very narrow."

European Commission's Head of Task Force for Relations with the United Kingdom Michel Barnier, centre, arrives to the main chamber of the European Parliament in Brussels. Picture: AP Photo/Francisco Seco

He said he was being "frank with you and open and sincere" when he said that he was unable to say what the result will be from the "last home straight of negotiations".

The Prime Minister and Ms von der Leyen took stock of negotiations in a call on Thursday evening.

The EU chief acknowledged "big differences" remained between the two sides and stressed that "bridging them will be very challenging".

Mr Johnson tweeted after the call to say he told Ms von der Leyen that "time is short and the EU position needed to change substantially".

Downing Street said the Prime Minister warned it looked "very likely" a deal would not be agreed unless the bloc shifted its stance.

Agreement was getting closer on the "level playing field" to ensure neither side could unfairly compete by eroding environmental standards, workers' rights or state subsidies, but fishing policy remained a major sticking point.

Mr Johnson warned the UK "could not accept a situation" where it was unable to control access to its waters and would have fishing quotas that "hugely disadvantaged its own industry", according to a No.10 spokeswoman.

"The EU's position in this area was simply not reasonable and if there was to be an agreement it needed to shift significantly," she said.

Mr Barnier's counterpart at No.10, Lord Frost, warned that progress "seems blocked" ahead of talks resuming in Brussels.

"The situation in our talks with the EU is very serious tonight. Progress seems blocked and time is running out," he tweeted on Thursday.

Cabinet Office minister Michael Gove, who has been in charge of the Government's no-deal planning, said on Thursday that the chances of an agreement remained "less than 50%".

He told the Commons Brexit committee the "most likely outcome" was that the transition period would end on December 31 without a deal.