LONDON — U.K. negotiators are not planning to present their own estimate of financial obligations owed to the EU on Brexit during this week’s round of negotiations, according to a U.K. official familiar with the progress of talks.

Despite warnings from EU diplomats that chief negotiator Michel Barnier is prepared to “stall” talks unless proposals are put forward by the U.K., the British side views this week’s round of talks as an opportunity to interrogate the EU’s position, the official said.

Their stance is consistent with U.K. Brexit Secretary David Davis’ statement to a House of Lords committee that the “proper approach to get the right outcome in the negotiation” would be to “challenge” the EU’s calculations. Davis told the committee last week the U.K. “may well publish an alternative proposal,” but the official, speaking on condition of anonymity, was clear this would not happen this week. It is not clear when an alternative will be published by the U.K. government.

Davis told the House of Lords EU committee last week that British officials had been engaged in interrogating the EU’s position on the so-called Brexit bill “on a line-by-line, almost word-by-word basis.”

“The objective in the case of the financial settlement is not to pay more than we need to, it’s fairly obvious,” he said. “There will be a process of challenge going on here and that will happen and has started already.”

“I would be tempted to say Article 50 negotiations are now in the hands of the divorce lawyers — we have very good divorce lawyers” — Margaritis Schinas

The EU side is insisting on a written acknowledgement from its negotiating partners of the need to settle the U.K.'s accounts with the bloc when it leaves. “We’re waiting for a position paper on financial settlement,” an EU official told POLITICO, adding that ideally it would arrive before the end of this round of talks on Thursday.

The Commission’s spokesman Margaritis Schinas said Tuesday that he would not provide “a running commentary” on the talks and declined to say if the British negotiating team had forwarded new position papers on topics such as the financial settlement.

"Talks are ongoing as we speak,” Schinas said, adding that the Commission will "assess this round of negotiations but it will not be done today or tomorrow, it will be done on Thursday.”

Asked whether Davis' early departure from the talks on Monday was viewed by the EU as a lack of seriousness he said: “I would be tempted to say Article 50 negotiations are now in the hands of the divorce lawyers — we have very good divorce lawyers.”

An EU diplomat who had been briefed on the talks said, “Barnier’s expectations going into the talks were very low, but even so he is quite frustrated so far,” adding that the lack of preparation of the British was beyond expectations on the EU side.

Another EU diplomat was more positive, predicting that Davis' acknowledgement in front of a House of Lords committee last week that the U.K. did have financial obligations would keep the talks on track.

"A stalling in this week's talks would only have arisen had there not been an acknowledgement on the U.K.'s financial obligations. Since they did make a statement I would imagine that the discussions will move forward."

'Go whistle'

There is a consensus among EU negotiators that the Brexit bill should be at least €65 billion, based on the U.K.’s share of the EU’s common budget, which has already been planned for up to 2020. Other EU diplomats predict the exit tab could climb to €100 billion or more if other, as yet undetermined, liabilities are also taken into account.

In London, the issue has become a political hot potato, with Brexit-supporting MPs in the ruling Conservative Party rejecting the need for a significant payment, and some hard-liners still insistent that Britain should pay nothing at all. Prime Minister Theresa May and Davis face a difficult balancing act if they are to meet the EU’s demand that financial obligations and other exit issues must be settled before substantial negotiations on the U.K.’s future trading relationship with the bloc can begin.

In a sign of the political difficulty facing May at home, Foreign Secretary Boris Johnson gave succor to colleagues in the party’s hard Brexit wing last week, when he branded EU estimates of the exit bill “extortionate” and invited Brussels counterparts to “go whistle.”

The difficult issue of border arrangements in Northern Ireland was discussed in the Brexit talks for the first time Tuesday. Both sides have decided the issue is so potentially fragile that it should be handled at a higher level than most of the other technical discussions — by talks directly between Sabine Weyand, deputy chief negotiator in Michel Barnier's Brexit Task Force, and Oliver Robbins, permanent secretary of the U.K. Department for Exiting the European Union.

There are not expected to be any technical solutions during this round of talks on how to resolve issues such as the free movement of goods and people over the border, according to an EU diplomat briefed on the talks.

"It's a bit of a scoping exercise. We don't know yet what the model will be and what the solutions on the ground will be," the diplomat said. "A political discussion needs to be had before the nitty-gritty details."

Talking trade

Separately, the talks have also touched on the issue of future trade arrangements. Officially, trade relations are not on the agenda of U.K.-EU discussions this week but the European Commission is increasingly keen to broach issues that are critical to its strategic trade interests, such as the post-Brexit allocation of import quotas.

WTO obligations — known as schedules — are also a concern to both parties. Schedules are a form of passport for taking part in international trade networks, mapping out a country's tariff and subsidy regimes. Schedules also form an important baseline for trade negotiations.

The goal is to agree a joint U.K.-EU proposal on schedules by the fall.

Britain's big challenge is that it currently trades under the EU's schedules and would not be able to draw up its own rulebook for entering the global trading system alone unless the remaining members of the 164-country WTO agree.

“The EU and the U.K. will engage in a series of meetings on WTO-related matters starting [during this week's Brexit negotiations],” an EU official said. "They will explore how to approach certain WTO-relevant issues relating to the withdrawal of the U.K. from the EU."

Speaking in Washington at the American Enterprise Institute, David O'Sullivan, the EU ambassador to the U.S., gave an indication Tuesday of the complexity of the Brexit talks. “Every day, frankly, in the course of going through this, our teams discover a further complexity that needs to be, one way or another, sorted out.”

But he added: “There is nothing punitive in the approach of the European Union to this process."

Giulia Paravicini and Katy O'Donnell contributed reporting.