With a chaotic and costly no-deal Brexit three weeks away, leaders of both the European Union and United Kingdom saw an ever liklier collapse of trade talks Thursday, and British Prime Minister Boris Johnson even spoke of a "strong possibility" of failure.

Both sides told their citizens to brace for a New Year's shock, as trade between the U.K. and the European mainland could face its biggest upheaval in almost a half century.

Johnson's gloomy comments came as negotiators sought to find a belated breakthrough in technical talks, where their leaders failed three times in political discussions over the past week.

Facing a Sunday deadline set after inconclusive talks between EU Commission President Ursula von der Leyen and Johnson on Wednesday night, both sides realized their drawn-out four-year divorce might well end on bad terms.

European Commission President Ursula von der Leyen welcomes British Prime Minister Boris Johnson in Brussels, Belgium December…
FILE – European Commission President Ursula von der Leyen welcomes British Prime Minister Boris Johnson in Brussels, Belgium, Dec. 9, 2020.

"I do think we need to be very, very clear: There is now a strong possibility — a strong possibility — that we will have a solution that is much more like an Australian relationship with the EU," Johnson said, using his phrasing for a no-deal exit.

Australia does not have a free trade deal with the 27-nation EU.

"That doesn't mean it's a bad thing," Johnson added.

On the EU side, reactions were equally pessimistic.

"I am a bit more gloomy today, as far as I can hear," Swedish Prime Minister Stefan Lofven said at an EU summit where von der Leyen briefed the 27 leaders on her unsuccessful dinner with Johnson.

weden's Prime Minister Stefan Lofven speaks during a news conference updating on the coronavirus disease (COVID-19) situation,…
FILE – Sweden's Prime Minister Stefan Lofven speaks during a news conference updating on the coronavirus situation, at the government headquarters in Stockholm, Sweden, Nov. 3, 2020.

"She was not really confident that all difficulties could be resolved," said David Sassoli, president of the EU parliament that will have to approve any deal brokered.

A cliff-edge departure would threaten hundreds of thousands of jobs and cost tens of billions of dollars in commerce.

To prepare for a sudden exit on January 1, the EU on Thursday proposed four contingency measures to make sure that at least air and road traffic would continue as smoothly as possible for the next six months.

It also proposed that fishermen should still have access to each other's waters for up to a year, to limit the commercial damage of a no-deal split. The plans depend on the U.K. offering similar initiatives. The move was indicative of how the EU saw a bad breakup as ever more realistic.

Fishermen empty a fishing net aboard the Boulogne-sur-Mer based trawler
FILE – Fishermen empty a fishing net aboard the Boulogne-sur-Mer based trawler "Nicolas Jeremy" in the North Sea, off the coast of northern France, Dec. 7, 2020. French fishermen net a quarter of their northeastern Atlantic catch in British waters.

Johnson warned that "yes, now is the time for the public and businesses to get ready for January 1, because, believe me, there's going to be change either way."

For months now, trade talks have faltered on Britain's insistence that as a sovereign nation it must not be bound indefinitely to EU rules and regulations — even if it wants to export freely to the bloc. That same steadfastness has marked the EU in preserving its cherished single market and seeking guarantees against a low-regulation neighbor that would be able to undercut its businesses.

After Johnson's midnight return to London, reactions were equally dim there.

U.K. Foreign Secretary Dominic Raab said the Sunday deadline was a "moment of finality" — though he added "you can never say never entirely."

British Foreign Secretary Dominic Raab speaks at a press conference with Secretary of State Mike Pompeo at the State Department…
FILE – British Foreign Secretary Dominic Raab speaks at a press conference at the State Department in Washington, Sept. 16, 2020.

In four years of talks on the U.K.'s departure terms and a future trade relationship, such self-imposed deadlines have been broken repeatedly since Britain voted to leave the EU.

January 1 is different because the U.K. has made the 11-month transition since its January 31 official departure legally binding.

"There are big ideological, substantive and policy gaps that need to be bridged," said Mujtaba Rahman, Europe managing director for the Eurasia Group. "They're so far apart and the time is so limited now."

A no-deal split would bring tariffs and other barriers that would hurt both sides, although most economists think the British economy would take a greater hit because the U.K. does almost half of its trade with the bloc.

Months of trade talks have failed to bridge the gaps on three issues — fishing rights, fair-competition rules and the governance of future disputes.

While both sides want a deal, they have fundamentally different views of what it entails. The EU fears Britain will slash social and environmental standards and pump state money into U.K. industries, becoming a low-regulation economic rival on the bloc's doorstep — hence the demand for strict "level playing field" guarantees in exchange for access to its markets.