Britain and E.U. Agree on a Plan for Brexit

Cabinet ministers will have a chance to review the draft text before a full cabinet meeting at 2 p.m. Wednesday, the prime minister’s office said.

Details of the agreement were not immediately available. Presumably, it contains language pertaining to the “backstop” plan to settle the contentious issue of the Irish border, the part of the agreement that is likely to set off the most sparks in the cabinet discussions.

The breakthrough followed months of discussions over the terms of Britain’s exit from the bloc, known as Brexit, an issue that has divided Britons and split Mrs. May’s governing Conservative Party. But the prime minister’s problems are far from over. In fact, they may be just beginning.

Even assuming she gains the cabinet’s approval on Wednesday without a politically damaging raft of resignations — not a given — Mrs. May faces daunting odds in pushing the compromise plan through Parliament, where it has many opponents.

Britain is scheduled to quit the European Union on March 29. The draft agreement, if approved, would at least avert the prospect of a disorderly and chaotic departure without any deal — something that could clog ports and lead to shortages of food and some medicines.

If Mrs. May’s cabinet signs off on the draft agreement, the next step is for European Union leaders to give it their blessing at a meeting at the end of the month.

It would then need the approval of the European Parliament and of British lawmakers in London. If that is forthcoming, the agreement would lead to a standstill transition period during which very little would change before the end of 2020.

However, Mrs. May cannot be certain of support from lawmakers in London because both hard-line supporters and opponents of Brexit have criticized her strategy.

Britons voted in 2016 to quit the bloc, in a simple yes-or-no referendum that offered no guidance on what sort of relationship should replace membership. Since then, Mrs. May’s government has been torn between those who want to keep close economic ties to the European Union in order to protect the economy, and those who want a clean break.

Many of those issues will remain unresolved until trade negotiations, which would take place during the transition period. An outline deal on those plans is expected to be reasonably vague.

In recent weeks, talks had stalled over the divorce terms to be spelled out in a withdrawal agreement, particularly over the backstop plan for the border between Northern Ireland, which is part of the United Kingdom, and Ireland, which will remain in the European Union.

Conservative, pro-Brexit hard-liners fear that a plan to prevent border checks might keep the United Kingdom tied indefinitely to European customs rules, preventing it from striking free trade deals further afield. They want a mechanism under which the government in London could quit unilaterally, something the European Union has adamantly resisted.

But there is opposition among pro-Europe Conservatives too, a fact that was underscored last week when Jo Johnson quit his post as a rail minister. Mr. Johnson — the brother of the pro-Brexit former foreign secretary Boris Johnson — campaigned to remain in the European Union. But in a withering resignation statement, he accused Mrs. May of drawing up plans that presented lawmakers with a choice between “vassalage and chaos.”

Nevertheless the conclusion of a draft deal is a big moment for Mrs. May.

For more than a year, she has tried her best to avoid confrontation with hard-line supporters of Brexit who oppose her strategy and want a clearer rupture with the European Union. Two pro-Brexit cabinet ministers have quit — Mr. Johnson as foreign secretary and David Davis as Brexit secretary — but most have remained inside the cabinet.

They now have to decide whether her compromise plan is good enough to keep their support.

One influential pro-Brexit lawmaker, Steve Baker, said on Tuesday that about 50 pro-Brexit Conservative lawmakers might oppose Mrs. May’s deal.

“What the prime minister is likely to ask us to support is not merely imperfect. It is to put us into a position that is worse than Article 50, worse than E.U. membership — less of a voice, more difficult to escape from.”

“It’s not kind of a grubby compromise that we can put up with and sort later,” he added. “It’s worse than membership.”