Theresa May will shut her most senior cabinet ministers away in a room until late Thursday night in an effort to force them to agree what kind of Brexit they want. But officials warn in private that the most divisive decisions may get kicked down the road.

The U.K. prime minister has invited her 11 most powerful colleagues to join her at her Chequers country house residence, where they will spend an afternoon, an evening, and at least one meal thrashing out the arguments over staying close to the EU’s rulebook, or breaking quickly away.

The meeting takes place against a fraught backdrop—her party is even more divided than her Cabinet, and without a parliamentary majority she can’t lay down the law. The risk of a leadership challenge hangs over everything May does. And she needs to spell out her blueprint for the future relationship with the EU now because talks on trade are due to start next month, and end in October.

Blurring the Details

By the end of the night, May’s aides hope she’ll have won enough support from her top team to be able to go away and write a speech she’s expected to deliver next week, announcing the U.K.’s negotiating goals.

“The prime minister is making a speech shortly in relation to the economic partnership and this is a significant part of that process,” May’s spokesman, James Slack, told reporters in London on Wednesday.

Privately, some in May’s team are cautious that a deal will be reached. One senior official said Wednesday that the meeting will be just another one of the series of discussions the cabinet has had on the subject. Another said there would be an exchange of views and discussion on the key points of contention. 

Ministers could agree, according to another official, to blur the details on the U.K.’s future relationship with the EU to preserve cabinet unity ahead of May’s speech.

But that won’t deal with the two biggest fears among cabinet Brexit supporters. These are that the riddle of avoiding a hard border with Ireland will be used as a Trojan horse to keep Britain in a customs union with the EU, and that May will allow the European Court of Justice to keep a role overseeing regulation affecting the U.K. after Brexit.

Brexit-backers and pro-Europeans in May’s cabinet have been holding meetings in pairs and small groups in an effort to reach a consensus. Their task became more complicated Wednesday when the government published its plans for the transitional period that businesses want to help bridge the gap between EU membership and life outside the bloc.

In the document, the U.K. asked the EU for flexibility on the length of the Brexit transition period so that it lasts as long as it’s needed. This is in contrast to the hard end date of Dec. 31, 2020 favored by the EU, and the move alarmed Brexit-backers in May’s party. The proposal wasn’t formally signed off by the Cabinet, according to an official.

Jacob Rees-Mogg, a leading Tory euroskeptic, registered his outrage at the document’s “perversion of democracy” in a column published by The Telegraph, highlighting the all-but-intractable divisions and sharp suspicions separating the factions within the party.

“Transition must be time limited,” Rees-Mogg wrote, which is at odds with the document’s talk of a duration “‘determined simply by how long it will take to prepare and implement the new processes’: this translates from bureaucratese into English: ‘we must remain.”’

Euroskeptic Tories worry May’s preparing to tie the country too closely to the EU’s single market and trade rules, an outcome they’d see as a betrayal of the U.K.’s 2016 vote to leave the bloc.

On Monday night, a letter emerged from 62 Brexit-supporting Tory lawmakers to the prime minister in which they demanded restrictions on any transitional terms that May agrees on. On the other side, pro-Europeans are fighting May’s plans to take Britain out of the EU’s single market and customs union.

To add to the prime minister’s troubles, her battle to get her Brexit laws through Parliament in preparation for the divorce is now raging in the U.K.’s upper chamber, the House of Lords, where she faces more opposition from her own side.