But May’s spokesman said the “focus is on getting this right” rather than meeting a deadline.

Diplomats and officials in Brussels note little progress in Brexit negotiations since the EU leaders last met, raising doubt about whether the bloc and London would be able to mark another milestone at the next top-level summit on June 28-29.

“We are concerned that there is no clear stance, no clear position from the British. The clock is ticking,” German EU Minister Michael Roth told his EU peers meeting in Brussels.

“We need now to be making substantial progress, but that is not happening. What is worrying us in particular is the Northern Ireland question where we expect a substantial accommodation from the British side.”

At home, May is stuck between a rock and a hard place with staunch Brexit supporters pushing to sever ties with the EU and others advocating keeping close customs cooperation with the bloc to reduce frictions in future trade.

May’s spokesman said London was working on two options for post-Brexit customs cooperation.

Under a customs partnership, Britain could collect tariffs on goods entering the country on the EU’s behalf. Under a second idea, for a streamlined customs arrangement, traders on an approved list would be able to cross borders freely with the aid of automated technology.

But the EU has said London must come up with a solution for the Irish border conundrum and highlights that has not happened. Both sides worry that reinstating a physical border between EU-member Ireland and Britain’s province of Northern Ireland - including to manage customs - could revive violence there.

Other outstanding issues include guarantees for expatriate rights, agreeing on security cooperation and trade rules after Brexit, to ensure a deal is in place when Britain leaves in March 2019, and an adaptation period ends at the end of 2020.

“From the European side, we can say that we have made clear our position and we hope that the British government will enter negotiations also in a full way,” said Austria’s Gernot Blumel, echoing a long-standing EU complaint that Britain has not made its position clear in detail on parts of the negotiations.

With May’s cabinet, her ruling Conservative party and the British split on the matter, that has proven difficult to achieve and the prime minister has come under increasing pressure at home in recent weeks to make a decision on customs.

The Brexit schedule is tightening, sources said, which helps the EU negotiating strategy to pile pressure on London before the June summit but mostly is due to lack of substantial headway in the talks.

Dutch Foreign Minister Stef Blok said it was too early to discuss an extension of the timeline, but added: “The aim is now to conclude a deal in the time schedule that has been agreed on ... I very much hope we will agree but there are no guarantees, unfortunately.”

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