Theresa May’s hopes of delivering Brexit could hinge on intensive efforts to persuade the Democratic Unionist Party to back the Withdrawal Agreement.
The 10 DUP MPs are viewed by Downing Street as crucial, not just for the votes they provide but the influence their stance has on Conservative Eurosceptics concerned about the Irish backstop.
The Prime Minister will not risk bringing her deal back to the Commons unless she is confident of avoiding a third humiliating defeat on the package.
Negotiations with the DUP are expected to continue on Monday, although Downing Street said a formal meeting is not scheduled.
Ministers have stressed that unless the deal is approved by MPs before Thursday’s summit of European Union leaders, the UK will be forced to accept a lengthy delay to Brexit.
That would require the UK to participate in May’s European elections and Mrs May warned it might result in Brexit never happening.
She said that if MPs did not back her deal before the European Council summit “we will not leave the EU for many months, if ever”.
As part of the effort to put pressure on Tory hardliners and the DUP, Chancellor Philip Hammond and International Trade Secretary Liam Fox made clear that the Prime Minister would not chance a third defeat on her deal after the 230-vote loss in January and last week’s 149-vote reverse.
Mr Hammond told BBC One’s Andrew Marr Show: “We will only bring the deal back if we are confident that enough of our colleagues and the DUP are prepared to support it so that we can get it through Parliament.”
Dr Fox told Sky News’ Sophy Ridge On Sunday: “I would say to my colleagues: all actions have consequences, and if you really want to deliver the Brexit we all promised… then we need to back the Prime Minister’s deal because there is no other deal on offer.”
He added: “If we had an extension with no agreement and this was just kicking into the long grass with the chance that Brexit might not happen at all, that would be very, very hard for most people to swallow.”
The possibility of Brexit being delayed or overturned in a second referendum is swinging some Eurosceptics reluctantly behind the deal ahead of a third vote on the package.
But so far the number of Tories publicly switching positions falls far short of the 75 MPs Mrs May needs to change sides.
Former foreign secretary Boris Johnson used his Daily Telegraph column to say that further changes were needed to the backstop, claiming it left the UK vulnerable to “an indefinite means of blackmail” by Brussels.
“If we agree this deal – and unless we have a radical change in our approach to the negotiations – we face an even greater humiliation in the second phase,” he said.
But he added: “There is an EU summit this week. It is not too late to get real change to the backstop. It would be absurd to hold the vote before that has even been attempted.”
Former Brexit secretary David Davis, who backed the deal last week, told The Times he might change his mind: “If they have not answered the Northern Ireland question properly I might not vote for it this time.
“I took them on trust last week. But now they have got to solve the problem.”
Bolton West MP Chris Green told BBC Radio 4’s Westminster Hour: “I want to vote against it because I don’t believe when Parliament defeated it by the biggest margin in the history of Parliament that was because it was in any way a good deal, and the substance of the deal hasn’t changed.”
But he added that a shift in the DUP’s position would have a “big impact” and the implications of rejecting the deal for a third time weighed heavily on him “because it could lead to a general election, and we don’t know how that will pan out”.
Other Tories made clear that the price for support could be Mrs May saying she will quit once the deal is through.
Conservative MP for Dover Charlie Elphicke said there needs to be “a change of leadership” in order for him to support the deal, telling BBC Sunday Politics South East we need “a new face and a new team to take us forward to the future relationship”.
Former Cabinet minister Esther McVey told the BBC: “She needs a dignified departure.”
Fellow Tory Andrew Bridgen told The Sunday Times: “I’ve been approached by whips offering the PM’s resignation if I vote her deal through.”
Ribble Valley MP Nigel Evans said Mrs May would have to go if there was a lengthy delay to Brexit.
“She promised to become Prime Minister to deliver what the 17.4 million people voted for, that is what she has to deliver and if she can’t do that, she has to go.”
Labour leader Jeremy Corbyn will have a series of meetings with other Westminster leaders including the SNP’s Ian Blackford and Liberal Democrat Sir Vince Cable and influential backbenchers in an effort to find a consensus on a rival Brexit strategy.
The Opposition could back an amendment to the deal calling for it to be pushed to a referendum, although Mr Corbyn said he was “not supporting Theresa May’s deal at all”.
Mr Corbyn said his meetings this week were “what the Government should have started two years ago – namely reach out, engage and listen to different views and find a consensus on Brexit which helps bring our country back together”.