Prime Minister Theresa May risks another humiliating Brexit defeat at the hands of her own eurosceptic MPs on Thursday, with just weeks to go until Britain officially leaves the EU.
Parliament will hold a symbolic vote calling for May to renegotiate her deal's unpopular "backstop" provision and also to rule out leaving the European Union without a deal, as agreed in House of Commons votes last month.
But eurosceptics in the Conservative party's European Research Group (ERG) could abstain from the vote, threatening defeat for May.
"Conservative MPs really ought not to be associated with anything, express or implied, which seems to take no deal off the table," said leading ERG member Steve Baker.
"Compromising no deal would be the daftest negotiating strategy and not in the national interest."
He criticised the government for making MPs vote on whether to support both measures agreed by parliament last month - even if they disagree with one - or hand their own government an embarrassing defeat.
A senior source within the ERG said the group would abstain, according to the Daily Telegraph, which would spell almost certain defeat for May given Labour's opposition to the motion.
But leading Brexiteer Liam Fox warned colleagues that such a result would raise doubts about whether a renegotiated deal could get through parliament, making the EU less likely to make on offer.
"Our European partners will be watching our debate and listening today to see if they get the impression that if they were to make those concessions parliament would definitely deliver," trade minister Fox told BBC Radio 4.
"There's a danger that we send the wrong signals."
Talks at 'crucial stage'
May's initial deal was roundly rejected by British MPs last month, but later parliamentary votes suggested a slim majority for her deal if she could get rid of the backstop clause.
The provision is intended to keep the border with Ireland free-flowing but some fear it could leave Britain trapped in EU trade rules indefinitely with no withdrawal mechanism.
British officials have since held a series of meeting with EU counterparts, who have ruled out reopening negotiations.
"The talks are at a crucial stage. We now all need to hold our nerve to get the changes this house requires and deliver Brexit on time," May told lawmakers on Tuesday.
"Having secured an agreement with the EU for further talks, we now need some time to complete that process," she said.
The announcement was seen by political commentators as an attempt to stave off the threat of parliamentary rebellion, with MPs now having to wait until February 27 for another series of votes on what to do if no agreement is reached.
Business leaders and economists have warned of shockwaves around the continent if no transition deal is in place when Britain leaves the EU.