“Nothing is off the table” when it comes to reassuring MPs over the Northern Ireland backstop, Downing Street sources say.
This could include reopening the EU withdrawal agreement, even though that comes with risk, the sources say.
Theresa May is understood to be pushing the EU for flexibility on the backstop, and whether it is temporary.
The BBC’s Political Editor Laura Kuenssberg said this was a change in tone from No 10.
The prime minister has previously insisted the withdrawal agreement she reached with the EU was locked.
Mrs May is set to hold private meetings with Tory backbenchers ahead of the crucial Commons vote on her deal on Tuesday. The withdrawal agreement has been endorsed by EU leaders but now needs Parliament’s backing.
Mrs May has warned her MPs that a rejection of her deal could lead to a general election – or possibly “no Brexit” at all.
The government is widely expected to lose Tuesday’s vote, with Labour, the Liberal Democrats, the DUP, the SNP and dozens of Conservative MPs saying they cannot support the deal.
Newspaper reports over the weekend said the vote would be delayed – but Number 10 insists it will go ahead as planned.
“The vote is going ahead,” Environment Secretary Michael Gove told BBC Radio 4’s Today programme.
He said the prime minister was “seeking to improve” the withdrawal agreement but there were “risks” involved.
“If we do attempt a fundamental reopening or renegotiation of the withdrawal agreement European Union countries, who recognise just how uncomfortable the backstop is for them, may change the withdrawal agreement in a way that may not necessarily be to our advantage,” he told Today.
He said it was “extremely unlikely” that he would mount a Tory leadership challenge if Theresa May stood down or was forced out after losing Tuesday’s vote.
Media captionBoris Johnson said it was a “relatively simple job” to change the withdrawal agreement
Foreign Office minister Sir Alan Duncan appealed to his colleagues on Monday morning to back the deal, telling BBC Radio 4’s Today programme they had not “thought strategically enough about the consequences”.
He echoed Mrs May’s warning of a general election if the deal was voted down, or a possible leadership contest, and said it could “set in train a course of events which could lead to chaos in many, many areas”.
But former Cabinet minister and Leave campaigner Theresa Villiers told the programme that the UK could cope with a no-deal scenario if “preparation is stepped up” and the EU co-operated.
Downing Street believes most Conservative MPs could support Mrs May’s deal if it were not for the backstop – the insurance policy designed to prevent a hard border in Ireland.
On Sunday evening, Mrs May spoke on the phone to Irish Prime Minister Leo Varadkar, whose support could be vital if she were to negotiate further with the EU.
She also spoke to the European Council President Donald Tusk, who tweeted it would be “an important week for the fate of Brexit”.
Boris Johnson said Mrs May could stay on if she lost Tuesday’s vote – but must renegotiate the deal with Brussels.
