LONDON -- WHAT'S HAPPENING

Prime Minister Theresa May is trying to renegotiate Britain's divorce deal with the European Union, after Parliament voted to alter a contentious proposal for the Irish border. The move was a victory for May, who managed to unite the warring pro-Brexit and pro-EU wings of her Conservative Party and secure a majority in the House of Commons, two weeks after lawmakers overwhelmingly rejected her Brexit deal.

But EU leaders are adamant that the agreement can't be reopened, so May's chances of success look slim.

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WHAT'S NEXT

May thinks she can win Parliament's support for the deal if changes are made. She will likely travel to Brussels in the next few days to press the bloc to help her. She has promised to return to Parliament by Feb. 13, either with a reworked version of the deal or with a statement on what she plans to do next.

By law, Britain will leave the EU on March 29. If a deal is in place, very little will change immediately. Britain will remain inside the EU's rules and institutions during a transition period until a new trading relationship is in place.

If there is no deal, existing trade agreements with the EU will evaporate overnight. Many businesses fear economic chaos, and warn of shortages of foodstuffs and other essential supplies.

Parliament is divided over Brexit, but most members oppose leaving without a deal, and on Tuesday they approved a motion ruling out a "no-deal" Brexit. But the vote is not legally binding, and Parliament also defeated tougher measures that tried to give lawmakers concrete powers to stop Britain crashing out of the EU, either by finding a new plan or by postponing the departure date.

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THE BACKDROP

The crisis has been building since Britain voted in 2016 to leave the 28-nation EU. In March 2017, Britain triggered the official two-year countdown to exit, and in November 2018 May's government and the EU sealed a legally binding withdrawal agreement.

The agreement must be approved by the European and British parliaments — and British legislators on both sides of the Brexit divide hate the deal, a compromise that keeps Britain outside the EU with no say but still subject to the rules and the obligations of membership at least until the end of 2020.

Opposition centers on a section of the deal known as the backstop, which would keep the U.K. in a customs union with the EU in order to remove the need for checks along the border between the U.K.'s Northern Ireland and EU member Ireland. Pro-Brexit lawmakers fear it will trap Britain in regulatory lockstep with the EU, and want the backstop replaced with unspecified "alternative arrangements."

The border is crucial to the divorce deal because it will be the only land frontier between the U.K. and the EU after Brexit, and because the free flow of people and goods underpins both the local economy and Northern Ireland's peace process.

Solving the intractable border problem is key to securing an orderly British exit from the EU.

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