It was a Twitter post worthy of that other Donald.

European Council President Donald Tusk blasted British Prime Minister Boris Johnson, accusing him of engaging in a "stupid blame game" on Brexit and demanding to know the U.K.'s intentions.

While Tusk's question in Latin was quo vadis — "where are you going?" — the question in English was more: "whoa, what is this?"

Tusk's Twitter post came early Tuesday afternoon while he was in Berlin meeting German Chancellor Angela Merkel to prepare for next week's European Council leaders' summit, which will focus in part on Brexit, but with the EU27 still deeply uncertain about how Johnson plans to proceed.

.@BorisJohnson, 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. You don’t want a deal, you don’t want an extension, you don’t want to revoke, quo vadis? — Donald Tusk (@eucopresident) October 8, 2019

It also came as Johnson's negotiator, David Frost, was in Brussels continuing to answer technical questions from EU negotiators about the proposal that the U.K. put forward last week. That advanced a complex customs and regulatory arrangement to manage the Ireland-Northern Ireland border in place of the backstop provision that was negotiated by Johnson's predecessor, Theresa May.

The EU27 still see that backstop, which would keep the entire U.K. in the EU's customs territory in the event that a free-trade deal is not reached by December 31, 2020, as the only workable solution for managing the Irish border. EU officials have insisted that they are still studying the proposal, which they say has numerous flaws. The EU says it needs answers to its questions before resuming formal negotiations.

Many diplomats and officials in Brussels fear that Johnson is angling to blame the EU if and when a deal proves unreachable while also laying the groundwork for his campaign in what is seen as an inevitable national election in the U.K. But Tusk's statement was unusually blunt and provocative — effectively declaring aloud that he does not regard the U.K. proposal as having been made in good faith.

It followed a briefing from the U.K. side of a phone call between Johnson and Merkel on Tuesday morning, which all but accused the German chancellor of ending the negotiations. A Downing Street official briefed some journalists that the German leader told Johnson the U.K. cannot leave the European Union without leaving Northern Ireland in a customs union with the EU. That "means a deal is essentially impossible not just now but ever," the official said.

Under Johnson's plan, Northern Ireland, like the rest of the U.K., would leave the EU's customs union following a transition period — on January 1, 2021. At that point, if a free-trade deal is not in place, the complex new customs and regulatory regime would enter into force, provided that Northern Ireland's devolved government agreed.

The U.K.'s proposal would establish a new customs border, as well as a new regulatory border — effectively creating two administrative borders. The EU's long-standing red lines in the negotiation insist on no such borders existing on the island of Ireland.

Irish Foreign Minister Simon Coveney quickly weighed in to support Tusk, while stressing that the EU was still open to negotiating a deal. "Hard to disagree," he tweeted, "reflects the frustration across EU and the enormity of what’s at stake for us all."

Meanwhile, the European Commission’s chief spokeswoman, Mina Andreeva, pushed back on assertions that talks had broken down.

“What I can reiterate is that the EU position has not changed,” Andreeva said. “We want a deal, we are working for a deal with the United Kingdom, and under no circumstances will we accept that the EU wants to do harm to the Good Friday Agreement. The purpose of our work is to protect it in all its dimensions, and at all times.”

Andreeva added, “Technical talks are continuing today, so I don’t see how talks could have actually been broken down, if they are happening today, and in the days to continue.”

She urged journalists at the Commission’s midday press conference to wait for comment from the German chancellery before jumping to conclusions about the Merkel-Johnson phone call on Tuesday morning.

Lili Bayer contributed reporting.