European Union and British negotiators remain locked in crucial talks to strike a Brexit trade deal but a solution over fishing rights appears to have faltered.
Nine months of negotiations are down to the last nine days with the deadline for the transition period falling on December 31.
The European Union’s chief negotiator Michel Barnier said the bloc is focused on a "final push", but fishing rights and who has access to which waters remains a sticking point.
Senior diplomats believe a deal could be signed before Christmas if the British are prepared to compromise on fishing rights.
“Differences on fisheries remain difficult to bridge. Unfortunately, the UK is not moving enough yet to clinch a fair deal on fisheries," one diplomat said.
"There is still serious concern on the level playing field and blockage on fish," said another senior diplomat. "For EU member states, the last commission offer already goes very far and can only be considered ... as final."
Mr Barnier told the closed-door gathering of ambassadors that the UK's latest offer on sharing out the catch from 2021 was "totally unacceptable", according to a source.
However, Prime Minister Boris Johnson, who campaigned for Brexit in a 2016 referendum arguing that it would restore Britain's sovereignty, has repeatedly said the country must control its own waters.
Earlier in the day, EU officials said an agreement was getting closer but it might not come together in time to be enforced on January 1. Without a deal, Britain's links to the EU will end with new tariff barriers in place.