British Prime Minister Theresa May could face a defeat 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 of 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 governing Conservative Party are angry over what they say is her acceptance of ruling out a no-deal departure, something May and her team deny, saying 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 in the country’s biggest political and trade policy shift in more than 40 years.

A rebellion, even in a symbolic vote, would be a blow to May, who has insisted to EU leaders that if they offer her more concessions to the deal agreed in November, she can command a majority in parliament and get the agreement passed.

Trade minister Liam Fox urged lawmakers to back the prime minister, warning: “Our European partners will be watching”.

A government source put it more bluntly. “Without support from MPs (Members of Parliament), it will be harder for the government to get the changes to the backstop we know they want,” the source said.

Steve Baker, a member of the pro-Brexit European Research Group of Conservative lawmakers, said no lawmaker in the governing party could associated with anything which seems to take a “no-deal Brexit” off the table.

“Compromising no deal would be the daftest negotiating strategy and not in the national interest,” he said on Twitter.

One Conservative MP said the ERG was still discussing which strategy to pursue on Thursday – to vote against or abstain.

May is trying to secure changes to the backstop arrangement to prevent a return of border controls between Northern Ireland and EU-member Ireland to ease concerns that Britain will be kept too closely in the EU’s orbit indefinitely or that the British province will be split away.

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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 to choose between backing her deal or leaving without an agreement.

Many businesses say that outcome would be catastrophic for the world’s fifth largest economy by 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 does not back a second vote.

To try to prevent a no deal, several lawmakers will try to get parliament to back their alternative proposals on Thursday, with options including a second referendum, a delay to Brexit and even a push to reverse the decision to leave the EU.

It is not clear whether any will win enough support to pass, with lawmakers who are seeking to force the government to delay Brexit saying they will wait until the next round of votes May has promised on Feb. 27 to make their move.