Brexit Minister David Davis (left) and European Union Chief Negotiator in charge of Brexit negotiations with Britain Michel Barnier (right) met for negotiations in Brussels on July 17, 2017, with Davis walking out of the proceedings early | Thierry Charlier/AFP via Getty Images Michel Barnier prepared to ‘stall’ Brexit talks over UK bill EU negotiators grow frustrated with what they see as lack of preparedness on the British side.

The EU's chief negotiator, Michel Barnier, is prepared to "stall" Brexit talks over the British government's unwillingness to present proposals for calculating the U.K.'s financial obligations, according to two EU diplomats.

On Monday, the first day of full-scale Brexit negotiations, EU officials voiced mounting frustration over the U.K.'s apparent lack of preparedness for serious negotiations.

The two EU diplomats briefed on the internal deliberations said Barnier was preparing to issue a warning on Tuesday to his British counterparts that he will stop talking over their refusal to make a counter-proposal on the Brexit tab, which could run to €100 billion.

According to the diplomats, the message Barnier planned to deliver, while not quite an ultimatum, was intended to convey his view that negotiations were futile without better engagement by the British side.

“Financial settlement is the priority," one EU diplomat said. "The EU will not walk away from talks but will stall them." The diplomat added, “The impression we got so far is that the U.K. is not ready for these talks."

“The impression we got so far is that the U.K. is not ready for these talks" — EU diplomat briefed on internal deliberations

Another EU diplomat said: “It is reasonable to expect the Brits to say something other than 'we will not pay a penny.' If that's not the case, what is there to talk about?” Last week, Foreign Secretary Boris Johnson told the House of Commons the EU could "go whistle" if it expected the U.K. to pay some of the sums that have been quoted in the press.

When asked directly whether Barnier was preparing to stall the talks over the Brexit bill, a spokesperson for the European Commission said it would not comment while the current round of talks is ongoing. The spokesperson did confirm, though, that a working group on the U.K.'s financial settlement had convened as planned.

Meanwhile, it was David Davis, the U.K.'s Brexit secretary, who walked out early on Monday — not in anger but, his officials insisted, as part of a pre-arranged plan. It may also have been useful for the government to have him in Westminster as the Conservatives faced a tight vote in parliament on procedural matters. That vote was a reminder of how tenuous the Tories' grip on power remains after losing their overall majority in last month's general election.

Davis appeared at the European Commission headquarters on Monday morning for a brief handshake and photo with Barnier and issued a short statement before immediately returning to London. The week's agenda is due to include the rights of EU citizens in the U.K. (and vice versa); the U.K.’s financial obligations to the EU; other separation issues; and the Northern Ireland border.

The U.K.'s Department for Exiting the European Union said that it had been the plan all along for Davis to open the negotiations, leave his team to handle the detailed talks and return to Brussels on Wednesday afternoon. They said the dealings in parliament, where Labour forced an emergency debate, were not a factor.

In a statement, the department said Davis' departure was “entirely consistent with all international negotiations, including the G7 and G20" and U.K. officials said Barnier would also be absent from talks until Thursday — though Barnier's schedule showed he would be in Brussels, if not sitting directly at the bargaining table, then certainly not far away from it.

'Thick as mince'

Whatever the explanations, the optics could hardly have been worse for the British side, creating an impression that Davis was not fully engaged in the historic talks, which hold enormous consequences for the U.K.'s political and economic future.

Pictures from the photo-op showed Barnier and two other EU negotiators with stacks of briefing files in front of them, sitting across the table from Davis and two U.K. negotiators who had not pulled out any paperwork.

And the swift departure of Davis from Brussels drew as much, if not more, criticism in the U.K. as in Brussels.

Labour's shadow Brexit secretary, Keir Starmer, said the government was in disarray over the Brexit talks.

“The clock is ticking and the risks are increasing day by day," he said. “David Davis can hardly say this is the time 'to get down to business' and then spend only a few minutes in Brussels before heading back to Whitehall."

Labour's shadow Brexit secretary, Keir Starmer, said the government was in disarray over the Brexit talks.

Dominic Cummings, the former campaign director of the Vote Leave campaign, blasted Davis in a post on Twitter, calling him: "thick as mince, lazy as a toad, & vain as Narcissus."

Liberal Democrat MP Tom Brake, who is his party’s Brexit spokesman, accused the government of having “no papers, no plan and no time.”

“They are meant to be negotiating Brexit but they can’t even negotiate among themselves,” Brake said.

The U.K. last week acknowledged that it faces some financial obligations upon its departure from the EU but officials have not come forward with a methodology for calculating them — unlike the EU, which laid out its approach in a briefing paper last month.

One EU official directly involved in setting Brexit negotiating strategy said last week's acknowledgment from London represented a step forward, but that it was not sufficient.

"Now we need this commitment to 'solidify' at the political level and during working groups this week," the official said in a text message. Without it, the official suggested, the talks could not get far.

“If the U.K. is not committed to acknowledging its obligations, then there is no real conversation on this topic, which will jeopardize progress on the talks for the entire first negotiating phase,” the official said.