Mr. Johnson and Ms. von der Leyen were expected to speak again at lunchtime on Sunday to take stock of the negotiations and make a decision about how to proceed.
Europe’s two most powerful leaders, Chancellor Angela Merkel of Germany and President Emmanuel Macron of France, both refused to engage directly with Mr. Johnson, effectively denying him the opportunity to exploit any divisions between the 27 members of the European Union.
With the odds of failure escalating, London and Brussels engaged in a mixture of finger-pointing and contingency planning. Mr. Johnson met with Michael Gove, the British minister in charge of preparing for a no-deal Brexit. Among the plans is the deployment of Navy patrol ships to halt foreign vessels attempting to enter the exclusive economic zone that extends 200 miles from the British coast.
The prospect of a military confrontation between British and French ships on the high seas provoked alarm and fierce criticism in Britain, even among members of the Conservative Party establishment.
“This isn’t Elizabethan times anymore; this is global Britain,” Tobias Ellwood, chairman of the defense committee in the House of Commons, said to the BBC. “We need to be raising the bar much higher than this.” A failure to reach a trade deal, Mr. Ellwood said, “would be a retrograde step, a failure of statecraft.”
Chris Patten, a former chairman of the Conservative Party and governor of Hong Kong from 1992 to 1997, accused Mr. Johnson of being on a “runaway train of English exceptionalism.” The prime minister, he added, was “not a Conservative,” committed to alliances, institutions or the rule of law, but an “English nationalist.”
Analysts said they had not given up hope of a last-minute agreement. Mr. Johnson and his advisers would still prefer a deal, as would the leaders of the European Union. Sunday, they noted, was the latest of multiple deadlines set by the two sides. The talks could easily stretch beyond then, all the way until New Year’s Eve.
Still, Britain’s strategy to wait until the end of the negotiating period and then push for major concessions appears to have backfired. European negotiators, driven by the French, have been firm on the issue of fishing rights, as well as on another contentious area: state aid to industry and competition rules.
Mr. Johnson has framed Britain’s campaign as an assertion of its sovereignty after leaving the European Union. But diplomats pointed out that European officials held a similarly strong point of principle: defending the integrity of the single market from a new competitor that sits on its doorstep.
“What the U.K. never understood is that the European Union is a political project,” said Kim Darroch, who served as Britain’s permanent representative to the European Union and, later, as ambassador to Washington. “They are going to make decisions based on political, not economic, considerations.”