Chief EU Brexit negotiator Michel Barnier warned Wednesday he can not guarantee he will strike a trade deal with Britain, diplomats said, and the next few days will be crucial.

"We are quickly approaching a make or break moment in the Brexit talks," Barnier told a video meeting of European envoys, a diplomat said, in an account of the video talks confirmed by other sources.

"Intensive negotiations are continuing in London, but as of this morning it is still unclear whether negotiators can bridge the gaps on issues like level playing field, governance and fisheries," Barnier said.

Diplomats said Barnier thought the outcome of the eight months of talks would be decided in the next few days, possibly late on Thursday or Friday. 

UK officials do not recognise a formal deadline, but privately agree the next few days could be crucial.

One European diplomat said there was "frustration" among the member state envoys and that "for the moment, we're still not there." 

"As of today we're not able to say whether there will be an agreement or not," the diplomat added.

Barnier's early morning briefing to envoys came after certain member states -- notably France and the Netherlands -- expressed concerns that the EU negotiation team was giving in too much to UK demands.

"This was mostly an exercise to calm nerves in Paris and elsewhere and to reassure member states that team Barnier will continue to defend core EU interests, including on fisheries," a third diplomat said.

Bridging the divide 

A diplomat from a country with concerns that Barnier might give too much ground, said: "I am not sure what Barnier said managed to assuage concerns. Bridging the divide would require too big a leap."

Barnier spoke to the EU27 officials by videolink from London, where he has been locked in intense talks with his UK counterpart David Frost and their teams.

Failure to clinch a deal would cause deep economic disruption between the two sides at a time when the European economy is already deep in a downturn due to Covid-19.

The main source of discord is over how to establish some sort of EU-UK alignment on health, labour and environment regulations, while also ensuring Britain's newly found sovereignty.

In addition, a few countries are especially worried about the fate of fishing access to British waters for European fishermen, with the UK wanting to keep tight control. 

Any deal would face ratification by EU member states as well as the British and European parliaments, a process that would begin after about two weeks of translation and legal scrutiny.

Barnier also briefed key MEPs on Wednesday who are highly reluctant to see their vote kicked to next year, possibly after the deal was implemented on a provisional basis.

"Swift progress is of the essence," said German MEP David McAllister, after European parliamentarians had their own video meeting with Barnier.

"An agreement needs to be reached within very few days if (member states) and Parliament are to complete their respective procedures before the end of the transition period. Democratic scrutiny is not negotiable," he said.