London, November 14: Prime Minister Theresa May will face a major showdown with her Cabinet ministers on Wednesday as the UK's withdrawal agreement with the European Union enters a crucial stage. Downing Street has said that the UK and the EU have agreed an initial draft agreement on the negotiating terms for Britain's exit, the so-called divorce settlement, from the economic bloc by March next year.

Theresa May now has the tough task of convincing her deeply divided Cabinet that the agreement is the best possible outcome for Britain. "The negotiations for our departure are now in the endgame. And we are working extremely hard, through the night, to make progress on the remaining issues in the withdrawal agreement, which are significant," May had said in a speech earlier this week.

"Both sides want to reach an agreement. But what we are negotiating is immensely difficult. I do not shy away from that," she said, hours before it emerged that Brussels was ready to publish a 500-page document of the withdrawal agreement once May is able to get her Cabinet on board. UK PM Theresay May Says Brexit Deal in Sight As Draft Is Agreed Upon.

On one of the most contentious aspects of the negotiations, the EU has reportedly dropped its demand for Northern Ireland to remain in the economic bloc's Customs Union as a "back stop" until a future trade deal is signed.

However, Prime Minister May is believed to have agreed that the region can remain more closely aligned to the EU regulations in some areas than the rest of the UK. The deal will involve a two-year transition until 2021, followed by a UK-wide Customs Union "backstop" in the event that the Irish border issue cannot be resolved during that period.

While the full details of the agreement are yet to be published, leading Brexiteers and even some pro-Remain MPs of the ruling Conservative Party have called on ministers to reject the deal as unacceptable.

Northern Ireland's Democratic Unionist Party (DUP), on whom May relies for her majority in the House of Commons, has warned that the agreement could lead to the break-up of the United Kingdom.

An embattled May hosted one-on-one briefings with her ministers in Downing Street on Tuesday ahead of the full Cabinet meeting expected to last around three hours later on Wednesday. Some key pro-Brexit ministers, including international development secretary Penny Mordaunt and work and pensions secretary Esther McVey, are being named as possible members of her Cabinet who might resign in protest and possibly even pave the way for a leadership challenge against May.

But May is thought to have won the support of five key ministers – foreign secretary Jeremy Hunt, home secretary Sajid Javid, Brexit secretary Dominic Raab, environment secretary Michael Gove, and Attorney General Geoffrey Cox.

If the Cabinet ends up signing off on the deal, the European Commission is expected to publish the details of the agreement alongside a much shorter declaration on future economic and security relations, which still need to be fully thrashed out.

Ambassadors from the remaining 27 EU member states will then discuss the possibility of organising an emergency summit later this month, earmarked for November 25, to sign off on it.

However, then the UK government faces a battle to win Parliament's backing on the divorce agreement, with some Tories already vowing to vote against it and the Democratic Unionist Party DUP's support being uncertain.

The crucial leg of the Brexit negotiations this week follows months of wrangles, with transport minister Jo Johnson becoming the latest minister to step down over the issue last week.

He followed in the footsteps of his brother Boris Johnson, who resigned as foreign secretary a few months ago and David Davis, who stepped down as Brexit secretary.

These ministers have vehemently opposed the withdrawal agreement and called on fellow Tory MPs to oppose it. "This is just about as bad as it could possibly be," Boris said, calling on ministers to reject the deal.

"This is the moment of truth. This is the fork in the road. Do we pursue a future as an independent nation or accept EU domination, imprisonment in the Customs Union and second class status. Cabinet and all Conservative MPs should stand up, be counted and say no to this capitulation," Davis said.

But Conservative Party Chief Whip Julian Smith, in charge of party discipline, has said he is "confident" the deal would pass. This critical stage of negotiations will determine the final stages of Britain's formal exit from the EU on March 29, 2019, after the June 2016 referendum in favour of Brexit.