Talk of a chaotic British split from the European Union grew on Tuesday with just three weeks left to break a deadlock in trade deal negotiations, as UK Prime Minister Boris Johnson warned that the two sides may have to accept “no deal”.

The EU’s chief negotiator, Michel Barnier, told a meeting of the bloc’s ministers that he believed a no-deal scenario at the end of the year was now more likely than an agreement on trade ties, an EU official and two diplomats told Reuters...