Boris Johnson is in a race against time to sell the Brexit deal he has struck with the EU to MPs ahead of a Commons vote on Saturday.
The prime minister insists he is “very confident” of getting the majority he needs to “get Brexit done” by his 31 October deadline.
But the DUP and every opposition party plans to vote against his deal.
That means he must persuade Labour rebels, ex-Tories and Brexiteers in his own party to get on board.
A spokesman for Mr Johnson said he and and his team were spending the day on the phone to MPs from across the Commons to sell the deal.
The PM will also hold a cabinet meeting in No 10 later.
The DUP’s Brexit spokesman, Sammy Wilson, said his party would not only vote Mr Johnson down, but urge Conservative MPs to “take a stand” with them, setting the scene for a frantic day of arm-twisting on all sides at Westminster.
The prime minister will make a statement to the Commons on Saturday, before another minister opens a debate on the deal.
If he does not manage to get the numbers needed to win a vote, then he is expected to try again to trigger a general election.
The law states that the PM must ask the EU for a three month extension to the Brexit deadline if he cannot get a deal through Parliament.
The text of the letter he must send to Brussels is contained in the so-called Benn Act, passed last month by MPs determined to prevent a no-deal Brexit.
Mr Johnson has said the UK will leave on 31 October with or without a deal – but he has also said he will abide by the law.
But even if MPs vote for his deal on Saturday, he may still have to ask the EU for an extension.
Former Conservative MP Oliver Letwin has tabled an amendment that would ensure the deadline is extended until the Brexit deal had passed each step in Parliament to become law.
Under the law as it stands, the government could have its deal approved in principle on Saturday and then leave with no deal anyway if it fails to pass implementing legislation by the 31 October deadline.
Sir Oliver, who is among the MPs seeking to prevent a no-deal Brexit, said he did not want to “let the government off the hook”.
The SNP’s Westminster leader Ian Blackford has also tabled an amendment, calling for a three month extension to Brexit to allow for an early general election.
He told the BBC says the deal gives Northern Ireland a “competitive advantage”, but “shafted” Scotland.
Meanwhile, cabinet ministers have been touring the TV and radio studios to sell the deal.
Foreign Secretary Dominic Raab told BBC Radio 4’s Today programme it was “an opportunity to get Brexit done, turn the page and move forward”.
The new deal is largely the same as the one agreed by Theresa May last year – but it removes the controversial backstop clause, which critics say could have kept the UK tied indefinitely to EU customs rules.
Northern Ireland would remain in the UK’s customs union under the new agreement, but there would also be customs checks on some goods passing through en route to Ireland and the EU single market.
The prime minister is expected to focus his attention on winning over three groups to support his deal:
- Tory Brexiteers who have not yet backed a deal and repeatedly voted against former PM Theresa May’s withdrawal agreement
- Twenty-three former Tory MPs who now sit as independents, including 21 Mr Johnson kicked out of the party last month after they rebelled against him in a bid to prevent a no-deal Brexit
- And a group of Labour MPs who have expressed a desire to back a deal but are concerned about protection for workers and the environment
The DUP is unhappy with the changes, claiming they are not in the best interests of Northern Ireland.
But the Northern Irish party can no longer rely on the rock solid support of the the pro-Brexit European Research Group – formed of backbench Tory MPs.
ERG member Andrew Bridgen told BBC Breakfast he believed the “vast majority” of the group “will come to the conclusion that this deal is tolerable and we need to get Brexit across the line”.
The ERG will hold a meeting on Saturday morning to advise a position to members to take in Parliament.
