UK PM Boris Johnson and EU chief Ursula von der Leyen to decide fate of Brexit deal

Britain's Prime Minister Boris Johnson and EU chief Ursula von der Leyen will hold another -- and probably, the last -- crisis call on Sunday to decide whether or not to abandon post-Brexit trade talks.

British negotiator David Frost met his EU counterpart Michel Barnier ahead of the leaders' call for last-ditch talks in the European Commission's Berlaymont headquarters in Brussels.

Sunday is just the latest in a string of supposedly hard deadlines for the negotiations but, with Britain due to leave the EU single market in 19 days, tensions are rising.

Johnson has said it is "very, very likely" the talks will fail, and EU officials have expressed similar pessimism, but British negotiator David Frost and his EU counterpart Michel Barnier carried on talking late into Saturday night ahead of Sunday's deadline.

On Saturday, Britain took the dramatic step of announcing that armed naval vessels will patrol its waters from January 1 to exclude European crews from the fisheries they have shared, in some cases for centuries.

Brussels' tone has been less bellicose, and von der Leyen has made it clear that the EU will respect UK sovereignty after Britain's post-Brexit transition period, but neither side is yet ready to compromise on its core principles.

Without a trade deal cross-Channel trade will revert to WTO rules, with tariffs driving up prices and generating paperwork for importers, and the failed negotiation may poison relations between London and Brussels for years to come.

On Wednesday, the EU chief said they had agreed to "come to a decision by the end of the weekend". Much of the text of a possible trade deal is said to be ready, but Britain has rejected Brussels' insistence on a mechanism to allow it to retaliate if UK and EU law diverge in a way that puts continental firms at a competitive disadvantage.

According to AFP, a spokesman for the Johnson government has stressed that Britain was ready to leave the union and handle its own affairs after 47 years of close economic integration and that "as things stand, the offer on the table from the EU remains unacceptable.

Earlier, Downing Street had said the government had a playbook that "maps out every single foreseeable scenario" for potential problems after December 31, and "no one needs to worry about our food, medicine or vital supply chains".