British Prime Minister Theresa May could be defeated in parliament on Thursday over her plan to renegotiate the Brexit deal, undermining her pledge to the European Union that, with changes, she can get the agreement approved.
Thursday's symbolic vote was seen by May's team as little more than a rubber stamp on her plan to secure changes to the divorce deal with the EU, giving her more time to satisfy lawmakers' concerns over one part of it - the Irish "backstop".
But hardline Brexit supporters in her Conservative Party are angry over what they say is her readiness to rule out a no-deal departure. May's Brexit minister Stephen Barclay again denied this in parliament, noting that, by law, Britain will leave the EU on March 29, with or without an agreement.
The latest twist in the two-year negotiation to leave the EU underlines the deep divisions in parliament over how, or even whether, Britain should leave the bloc - its biggest political and trade policy shift in more than 40 years.
A rebellion, even in a symbolic vote, would hurt May, who has insisted to EU leaders that if they offer her more concessions to the deal agreed in November, she can secure a majority in parliament.
"Colleagues should be in no doubt that the EU will be watching our votes tonight carefully for any sign that our resolve is weakening. We should not give them that excuse not to engage," Barclay told parliament as he opened the debate. Lawmakers are expected to vote from 1700 GMT.
"CLEAR MANDATE NEEDED"
A government source put it more bluntly: "Without support from MPs, it will be harder for the government to get the changes to the backstop we know they want."
An EU diplomat dealing with Brexit agreed, saying the bloc "needs her to have a clear mandate for talks".
But Steve Baker, a member of the pro-Brexit European Research Group of Conservative lawmakers, said no lawmaker in the governing party should be associated with anything that seemed to take a "no-deal Brexit" off the table.
One Conservative lawmaker said the ERG was discussing which strategy to pursue on Thursday after speaking to the government's chief whip, May's enforcer in parliament, and listening to Barclay. Two sources said the group would reach a decision later on Thursday.
The group's leader, Conservative Jacob Rees-Mogg, told ITV he thought it was unlikely that the Brexit supporters would vote against the government. Others said they might abstain, which could also condemn the government to defeat.
The backstop arrangement is designed to prevent a return of border controls between the British province of Northern Ireland and EU-member Ireland if, after a period of negotiation, the two sides cannot agree a trade deal that makes checks unnecessary.
Many Brexit backers in parliament fear that it will keep Britain in the EU's orbit indefinitely, or result in Northern Ireland being split away.
On Wednesday, European Council President Donald Tusk said the bloc was waiting for Britain to present solid proposals to break the impasse after meetings in Brussels and telephone calls between May and EU leaders.
Some Conservative and many opposition lawmakers accuse May of "running down the clock", edging Britain closer to the exit date to try to force parliament into a choice between backing her deal or leaving without an agreement.
Many businesses say that outcome would be catastrophic for the world's fifth largest economy: causing delays at ports, fracturing international supply chains and hindering investment.
More than 40 former British ambassadors called on the government to extend Britain's stay in the EU or allow for a second referendum, the Times newspaper reported. May has repeatedly said she will not back a second vote.
To try to prevent a no-deal exit, several lawmakers put down alternative proposals.
Parliament's speaker selected three to be voted on.
One calls for parliament to be given a vote on a revised Brexit deal or a debate on the next steps by Feb. 27; another seeks to delay Brexit for at least three months; and a third demands that the government publish an impact assessment of a no-deal departure.
Based on previous similar votes, the main opposition Labour Party is lkely to back the last proposal, increasing the likelihood that it will pass.
The real crunch date for the government looks set to come on Feb. 27, when May has promised the next round of votes. Lawmakers seeking to force the government to delay Brexit say that will be moment they make their move.