Theresa May is to issue a rallying call for MPs to "hold our nerve" as her battle to secure a Brexit deal backed by Parliament reaches a crucial stage.
The prime minister will update the Commons on Tuesday on the latest developments in negotiations with Brussels and Dublin, as the sides try to find a way through the impasse on measures for the Irish border.
Downing Street said Mrs May's statement, which comes a day earlier than expected, will give MPs more time to "digest the content" ahead of a series of expected Commons votes on Thursday.
Mrs May is expected to say: "The talks are at a crucial stage. We now all need to hold our nerve to get the changes this House has required and deliver Brexit on time.
"By getting the changes we need to the backstop; by protecting and enhancing workers' rights and environmental protections; and by enhancing the role of Parliament in the next phase of negotiations I believe we can reach a deal that this House can support."
Talks are continuing apace between the UK and EU, with Brexit Secretary Steve Barclay and Mrs May's de facto deputy, David Lidington, meeting MEPs in Strasbourg on Tuesday.
Mr Barclay was said to have held "constructive" talks on Monday night with the EU's chief negotiator Michel Barnier in Brussels.
The pair agreed to further meetings in the coming days, while their teams will continue to work to find a way forward.
Meanwhile, Sky News reported the former president of the European Council, Herman Van Rompuy, had dinner with Mr Lidington in Brussels on Monday night.
Mr Van Rompuy has been tipped as a potential "influencer" to break the Brexit deadlock, Sky News reported.
Negotiations of a kind have also been taking place back in Westminster, with an exchange of letters between Mrs May and Labour leader Jeremy Corbyn.
However a Cabinet minister insisted there is "no chance" of Mrs May accepting Labour's vision for leaving the EU, despite speculation she could soften her stance on customs union membership.
Commons leader Andrea Leadsom dismissed the prospect of Mrs May adopting Mr Corbyn's "world view".
Mrs Leadsom, an ardent Leaver, said she would stay in the Cabinet to help Mrs May deliver Brexit and denied that the PM was softening her stance over a customs union in a letter to Mr Corbyn.
Mrs May’s reply sparked concern among Conservative Brexiteers that the Prime Minister could concede too much ground to Labour in an attempt to win cross-party backing for a deal with Brussels.
Mrs Leadsom said: "I think she's making quite clear that what Corbyn is demanding is actually not as good as what the Prime Minister's deal is offering.
"So he wants a customs union and he is unclear as to whether that means he also wants an independent trade policy.
"He's unclear as to whether he also wants to stop free movement, and of course the EU’s view would be, 'well, if you're in the customs union then you have free movement and you abide by the common external tariff'.
"I think there's no doubt that what the prime minister is offering is better than what Corbyn is demanding, which simply begs the question, if they like it, why don’t they vote for it?"
Mrs Leadsom said there was "no chance" Mrs May would adopt Mr Corbyn's "view of the world", adding: "The prime minister has been absolutely clear we're leaving the EU, we're leaving the customs union, we're leaving the single market."
The frontbencher refused to say what the cut-off date would be for the necessary legislation to get through the Commons to allow the UK to leave the EU as planned on March 29.
She said it was possible to pass bills "quite quickly" with "goodwill" from the Commons and Lords, but added: "It's just not possible to say how quickly it could be done."