LONDON (AP) — Britain and the European Union traded ill-tempered barbs Tuesday as the U.K. said a Brexit deal might be impossible, while insisting it was still working for one with just over three weeks until its scheduled departure from the bloc.

British Prime Minister Boris Johnson's office said EU intransigence had led to a breakdown in negotiations, prompting a top European leader to warn against playing a "stupid blame game" — and chide Johnson in Latin.

Johnson's office gave a gloomy assessment after his call with German Chancellor Angela Merkel on Tuesday morning.

In a statement to British media, Downing Street said Merkel had told Johnson that "a deal is overwhelmingly unlikely" unless the U.K. agreed to let Northern Ireland continue to follow EU customs rules in order to maintain an open border with EU member Ireland.

That is something the British government says it can't accept. Downing Street said that "if this represents a new established position, then it means a deal is essentially impossible not just now but ever." How people and goods will move across the Irish border is the main sticking point to a deal.

The German government confirmed that Merkel and Johnson had spoken but declined to comment on the substance of "confidential conversations."

European Commission spokeswoman Mina Andreeva said "the EU position has not changed. We want a deal. We are working for a deal with the U.K."

European Council President Donald Tusk tweeted testily that "what's at stake is not winning some stupid blame game."

"At stake is the future of Europe and the UK as well as the security and interests of our people," he said, addressing Johnson. "You don't want a deal, you don't want an extension, you don't want to revoke, quo vadis?" — a Latin phrase meaning "where are you going?"

Despite the grim mood music, British officials insisted they still hope to strike a deal before Britain's scheduled Oct. 31 departure date — although Johnson has also said the U.K. will leave even if one is not struck.

"We've moved — it is now time for the EU to move too," said Michael Gove, the minister in charge of Brexit preparations. "If it does, then there is still every chance we can leave with a new deal."

Downing Street said Johnson spoke by phone to Irish Prime Minister Leo Varadkar on Tuesday afternoon, and "both sides strongly reiterated their desire to reach a Brexit deal." It said the two leaders hoped to meet in person later in the week.

EU leaders have demanded more "realism" from Britain in response to a Brexit plan proposed by Johnson. The bloc says the proposals — which would require customs checks on some goods moving between Northern Ireland and Ireland — don't fulfill the U.K.'s commitment to a frictionless Irish border.

An open border is key to both the regional economy and the peace agreement that ended 30 years of conflict between Catholics and Protestants in Northern Ireland. Northern Ireland is part of the U.K. but shares an island — and a land border — with the Republic of Ireland.

"It's not just about trade, it's about so much more than that, and anybody who understands Ireland and the politics of this island understands that," said Irish Deputy Prime Minister Simon Coveney.

French President Emmanuel Macron has said the EU will assess by Friday whether a deal is possible.

Johnson's opponents in Britain accused the government of deliberately undermining the Brexit talks.

"Boris Johnson will never take responsibility for his own failure to put forward a credible deal. His strategy from day one has been for a no-deal Brexit," said Keir Starmer, Brexit spokesman for the main opposition Labour Party.

On Tuesday, Britain published more details of its plans for leaving without a divorce deal. The government says those plans will minimize any resulting economic shock.

Economists and business groups warn that no amount of preparation can eliminate the pain of new barriers with the EU, which accounts for almost half of U.K. trade.

The government's "no-deal readiness report" shows significant British preparation but also acknowledges its limits. Britain says it will try to keep goods flowing by not immediately imposing border checks on imports from the EU. But the government acknowledges there will be new tariffs on 60% of British exports to the EU, including levies of more than 50% on beef and lamb.

Many in the EU — and in Britain — are skeptical that Britain will leave the bloc on Oct. 31 because the U.K. Parliament has passed a law compelling the government to ask the EU for a delay to Brexit if no deal is agreed upon by Oct. 19.

Johnson says he will obey the law but will not ask for a delay. It's not clear how those two statements can be reconciled — but it's clear Johnson wants to pin the blame for any delay on Parliament and the EU, so that he can campaign as a champion of Brexit in an election that's likely to be called soon.

Both the government and the opposition see a national vote as the only way to break Britain's Brexit deadlock, though they disagree on the timing.

Parliament is set to be suspended Tuesday evening so that a new session can begin next week with a major policy speech from Johnson's Conservative government.

An earlier attempt by the government to shut down Parliament for five weeks was ruled illegal by Britain's Supreme Court because it had the effect of preventing legislators from scrutinizing the government's Brexit plans. This week's shorter suspension is more routine. Lawmakers will return on Monday.

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Casert reported from Brussels. Associated Press writer Geir Moulson in Berlin contributed to this story.

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