European Commission President Ursula von der Leyen attends a press conference at the EU headquarters in Brussels on Sunday. On the same day, she had a phone call with British Prime Minister Boris Johnson agreeing to continue Brexit trade talks. Photo: VCG

Chief EU negotiator Michel Barnier on Monday signaled there was a "narrow path" to a post-Brexit trade deal with Britain, as key sticking points remain after both sides abandoned a supposed make-or-break deadline. 

British Prime Minister Boris Johnson and EU chief Ursula van der Leyen pledged on Sunday to "go the extra mile" as they sidestepped the self-imposed cutoff point to end talks if there was no progress toward a pact. 

Britain left the EU on January 31 ­after five decades of integration, but a transition period during which it remains bound by the bloc's rules ends on ­December 31.

Without a post-Brexit deal, Britain's trade with its biggest market would in future operate on pared-down World Trade Organization rules, including tariffs and quotas.

Johnson has insisted it remains "most likely" that Britain will crash out of the globe's largest single market by year's end as the two sides spar over regulating future standards and on fishing rights. 

But von der Leyen said Monday, "There is movement. That is good."  

"We are on the very last mile to go. But it is an essential one," she told a conference organized by the Organization for Economic Cooperation and Development.

An EU diplomat said following a briefing from Barnier that "there might now be a narrow path to an agreement visible - negotiators can clear the remaining hurdles in the next few days." 

But "substantial gaps still need to be bridged in important areas like fisheries, governance and level playing field," the diplomat said. 

An EU source said London had now accepted there should be a mechanism to regulate any future divergences in standards.

More serious blockages remain "on all fronts" on the issue of fishing rights, the source said. 

"If there is progress on fishing then we could have an agreement in the coming days," the official said. 

Johnson's official spokesperson did not say whether there had been any progress and insisted no deal remains a "possible outcome."