The European Union is likely to tell Theresa May that she must decide by mid-April whether to extend Brexit until 2020 or risk leaving in three months without a deal, a senior EU official said.
At a summit in Brussels on Thursday, leaders are likely to deliver an ultimatum that would give the British prime minister just three weeks to decide whether to gamble on getting the current Brexit deal through the British Parliament by July.
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If she decides she can, the EU is almost certain to deny any further request for a Brexit delay were she to fail, the official said. If she decides she can't, the EU is likely to grant an extension into next year.
May's Brexit strategy was thrown into disarray this week when the speaker of Parliament said she couldn't put her unpopular deal back to lawmakers for a third attempt unless she changed her proposal first. But EU officials are still maneuvering to try to help her get the agreement through Parliament - and see that as plan A.
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Like May, European officials have some hope that the prospect of a long delay will scare Brexit-backing politicians into backing her deal.
In an attempt to make a Brexit extension look unpalatable to pro-Brexit members of parliament, EU leaders are likely to insist that the current divorce deal can't be reopened even if the UK's departure is postponed by many months, according to the official. His comment was backed up by diplomats' notes of a meeting of EU ministers on Tuesday.
That would mean that even if Parliament votes against the deal and the UK delays Brexit for further negotiations, the much-hated Irish border backstop will remain. The UK will also be asked to pledge not to disrupt EU business or decisions during the extension, the official said.
Leaders will allow a long Brexit delay only if May sets out a clear explanation of how she will break the current parliamentary deadlock, EU officials said. This could be in the form of "a timetable to a new referendum or a new election," EU chief Brexit negotiator Michel Barnier told a meeting of European governments in Brussels on Tuesday, according to a diplomatic note.
This reflects a feeling among leaders that a long extension might pave the way to the UK changing its mind and staying in the bloc, the official said.
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"My feeling is that a longer extension needs to be linked to something," Barnier told reporters after the meeting. "There needs to be a new event; a new political process."
It's unclear whether Parliament Speaker John Bercow will consider a new agreement on an extension enough of a change to justify another vote. He hinted on Monday that some kind of new agreement with the bloc would be required.
In any case, leaders are prepared to make the extension offer contingent on a possible vote next week. If the deal is passed, the EU will grant a "technical" extension of two or three months to allow for outstanding legislation without conditions. If the deal fails, a longer extension will be required, and May will be pressed for new ideas.
Going into the summit in Brussels, patience with the UK was wearing thin. Member states don't want a no-deal, but many are keen to stop wasting resources on a country that's meant to be leaving.
"I don't have any appetite for substance-less, very abstract discussions and negotiations on Brexit," German Europe Minister Michael Roth told reporters. "Please deliver, dear friends in London, please deliver."