British Prime Minister Theresa May speaks during a media conference at the conclusion of an EU-Arab League summit at the Sharm El Sheikh convention center in Sharm El Sheikh, Egypt, Monday, Feb. 25, 2019. British Prime Minister Theresa May stays convinced that March 29 remains a realistic Brexit date, despite the EU urging Britain to delay its departure from the bloc to avoid a chaotic rupture. (AP Photo/Francisco Seco)

British Prime Minister Theresa May speaks during a media conference at the conclusion of an EU-Arab League summit at the Sharm El Sheikh convention center in Sharm El Sheikh, Egypt, Monday, Feb. 25, 2019. British Prime Minister Theresa May stays convinced that March 29 remains a realistic Brexit date, despite the EU urging Britain to delay its departure from the bloc to avoid a chaotic rupture. (AP Photo/Francisco Seco)

LONDON (AP) — Prime Minister Theresa May returned from a seemingly unproductive meeting with European Union leaders Monday to a growing attempt by British lawmakers to stop her from taking Britain out of the EU on March 29 without a divorce deal.

With May and the EU at odds over not just how, but when Brexit should happen, her political opponents were getting increasingly desperate to take control of Britain’s muddled departure from the bloc.

At an EU-Arab League summit in Egypt, the EU warned Britain it faces the prospect of delaying its planned March 29 departure or the consequences of a chaotic exit. European Council President Donald Tusk, who chairs meetings of EU nation leaders, said Monday it would be “rational” to postpone Brexit day.

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May insisted she intends for Britain to leave as planned in a little more than a month. But her often divided opponents may be coalescing around a plan to prevent Britain crashing out of the EU with no agreement in place.

The main opposition Labour Party took a big step Monday toward backing a new referendum on the country’s EU membership.

The party has previously said it would support a referendum as a last resort if it could not secure a new election or make changes to May’s EU divorce deal. Britain’s Parliament has so far rejected the deal struck between May’s government and the bloc, and is due to hold a series of votes Wednesday on next steps in the Brexit process.

Labour has proposed its own withdrawal plan as an alternative to the government’s deal with the EU. The party said Monday it would back a second public vote if the House of Commons rejects its plan this week, as is widely expected.

Labour leader Jeremy Corbyn said the party is committed to “putting forward or supporting an amendment in favor of a public vote to prevent a damaging Tory Brexit being forced on the country.”

The party did not specify what voters might be asked to consider in any future vote, though it has previously said the option of Britain remaining an EU member would be included.

Labour has previously said it would only support a second referendum as a last resort if it could not secure a new general election or make changes to May’s divorce deal.

The change in approach follows the resignations of nine Labour lawmakers last week, partly over the party’s failure to back another Brexit referendum. It is likely to cheer many party members, who have backed calls for a so-called “people’s vote.”

While there is little chance of a second referendum taking place without the support of Labour, the path to another Brexit vote is far from clear. It would require the support of numerous lawmakers from the governing Conservative Party, for example.

Since lawmakers rejected May’s deal with the EU last month, the prime minister has sought to get changes from Brussels on a provision for the border between the U.K.’s Northern Ireland and EU member Ireland.

The mechanism, known as the backstop, is a safeguard that would keep the U.K. in a customs union with the EU to remove the need for checks along the Irish border until a permanent new trading relationship is in place.

May wants to revise the deal to reassure opponents from her Conservative Party, as well as from a Northern Ireland party that props up her minority government, the backstop would only apply temporarily.

But EU leaders insist that the legally binding Brexit withdrawal agreement, which took a year and a half to negotiate, can’t be reopened.

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The impasse has raised concerns that Britain will leave the EU without a deal, a scenario that would likely mean new tariffs on British exports and serious disruption to trade between the two sides. The Bank of England has warned that the British economy could shrink by 8 percent in the months after a disorderly Brexit.

May has said a new vote on any revised Brexit deal won’t be held this week and could come as late as March 12.

A number of British lawmakers are seeking to wrest control of the process from the government and are looking to get support for an amendment that would require May to seek an extension to the Brexit date if Parliament fails to back her deal.

“I don’t see how businesses can plan. I don’t see how public services can plan, and I think it’s just deeply damaging,” Labour lawmaker Yvette Cooper, one of those behind the move, told the BBC.

On Monday, the EU’s Tusk warned that the chances of a withdrawal agreement being concluded in time are receding, and that sticking by the planned Brexit date would be too risky.

“I believe that in the situation we are in, an extension would be a rational solution,” Tusk told reporters at an EU-Arab League summit in Egypt after talks with May that he said included discussions over extending the Brexit process.

May insisted a deal in time was still possible.

“It is within our grasp to leave with a deal on 29th of March and I think that that is where all of our energies should be focused,” May said.

She said that “any delay is a delay. It doesn’t address the issue.”

Dutch Prime Minister Mark Rutte warned her against “sleepwalking” into a chaotic Brexit next month.

“It’s absolutely unacceptable. And I think your best friends have to warn you for that,” Rutte told the BBC. “Wake up. This is real.”

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Raf Casert in Brussels and Pan Pylas in London contributed.

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This story has been corrected to show nine Labour Party lawmakers, not eight, resigned last week.

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Follow AP’s full coverage of Brexit at: https://www.apnews.com/Brexit