Foreign Secretary Jeremy Hunt says “extra time” may be needed to finalise legislation for Brexit.
Mr Hunt said a possible delay in the UK’s departure from the EU beyond the 29 March deadline depended on the progress made in the coming weeks.
The PM is seeking “alternative arrangements” to the backstop, but the EU says it will not renegotiate.
Meanwhile, the government says Parliament’s week-long February half term break looks set to be cancelled.
Commons Leader Andrea Leadsom told MPs: “There are currently no plans to bring forward a motion to agree dates for a February recess.
“The House may therefore need to continue to sit to make progress on the key business before the House.”
Parliament had been due to rise for recess on Thursday, 14 February and return on Monday, 25 February.
The UK is due to leave the European Union at 23:00 on 29 March. The backstop is an “insurance” policy to stop the return of checks on goods and people along the Northern Ireland border.
Earlier this month, Ms Leadsom said that the EU may be prepared to grant the UK a “couple of extra weeks” beyond the 29 March deadline to finalise preparations for Brexit.
And BBC political editor Laura Kuenssberg said there had been “growing chatter” about a potential delay and a potential extension to Article 50 – the mechanism by which the UK leaves the EU.
But Downing Street has said an extension to Article 50 is not being considered and the government remains “committed to doing whatever it takes to have the statute books ready for when we leave the EU on 29 March this year”.
Mr Hunt told BBC Radio 4’s Today programme: “It is true that if we ended up approving the deal in the days before the 29 March, then we might need some extra time to pass critical legislation.
“But if we are able to make progress sooner, then that might not be necessary.
“We can’t know at this stage exactly which of those scenarios would happen.”
Theresa May has been talking to EU leaders, including President of the European Council Donald Tusk and the Irish Taoiseach, Leo Varadkar, after MPs voted on Tuesday for her to make changes to the backstop.
Mr Hunt said it was currently a “challenging situation” and the government was “not ruling out any of these potential solutions” to the Irish border issue.
Mr Hunt said the commitment to the Good Friday Agreement – which protects against the return of a hard Irish border – would need to be demonstrated.
The EU’s concerns that the UK could “access the single market by the back door” would also need to be alleviated, he said.
“If we can overcome those two issues, which I think we can, then we will be able to have substantive discussions,” he said.
“But this is not going to happen in the next few days.”
The backstop was one of the main reasons Mrs May’s Brexit deal was voted down in Parliament by a historic margin earlier in January as critics say a different status for Northern Ireland could threaten the existence of the UK and fear that the backstop could become permanent.
The prime minister has said there are several possible alternatives to the backstop that she wants to discuss with EU leaders.
- a “trusted trader” scheme to avoid physical checks on goods flowing through the border
- “mutual recognition” of rules with the EU
- “technological” solutions
She also wants to discuss a time limit on the backstop and a “unilateral exit” mechanism – both options ruled out by the EU in the past.
But the EU’s chief negotiator, Michel Barnier, has said the Irish backstop is “part and parcel” of the UK’s Brexit deal and will not be renegotiated.
Speaking at the European Parliament on Wednesday, Mr Barnier said it was a “realistic solution” to preventing a hard border.