- Video report by ITV News Political Correspondent Romilly Weeks
Theresa May says MPs will have another chance to vote against a no-deal Brexit on 27 February as she seeks to buy more time.
Her statement comes a day earlier than expected as negotiations continue in Brussels and Dublin.
Speaking in the House of Commons on Tuesday, she said if "the Government has not secured a majority in this House in favour of a Withdrawal Agreement, under political declaration, then the Government will on Tuesday the 26th February make a statement and table an amendable motion relating to the statement."
She added "a minister will move that motion on Wednesday 27th February enabling the House to vote on it and on any amendments to it on that day."
ITV News' Political Editor Robert Peston tweeted the day would be a "definitive date for MPs" to force Mrs May "to take a no-deal Brexit off the table."
In an attempt to rally support Mrs May told MPs: "We now all need to hold our nerve to get the changes this House requires 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.
"We can deliver for the people and the communities that voted for change two-and-a-half years ago - and whose voices for too long have not been heard.
"We can honour the result of the referendum."
In response to Mrs May's statement, Labour leader Jeremy Corbyn accused her of "running down the clock" in the hope that MPs will be "blackmailed" by the fear of a no-deal Brexit into supporting "a deeply flawed deal".
"This is an irresponsible act," said Mr Corbyn. "She is playing for time and playing with people's jobs, our economic security and the future of our industry."
Mr Corbyn accused Mrs May of refusing to listen to his alternative deal, involving a permanent customs union membership, a close alignment with the single market and matching EU workplace and environmental protections.
"I urge all members across this House to think about the damage the Prime Minister's strategy is doing - the threat to industry and skilled jobs in communities across Britain," he said.
Labour MP Yvette Cooper, Home Affairs Select Committee chairwoman, said a no-deal Brexit would "undermine national security".
She asked whether the Prime Minister would extend negotiations in that scenario, a question Mrs May didn't answer directly.
She instead insisted "the extension of Article 50 is not something which solves the problem" and urged MPs to back her deal.
Brexit Secretary Stephen Barclay said the Government is being "very clear" with European Leaders that a "legally binding" change to the backstop arrangement is required.
Mr Barclay said "Parliament needs to see legally binding change to the backstop. That was the clear message that was set out at the recent vote ... and that is what we have asked for.
"The key issue is that we need to deliver an outcome that is legally binding on the backstop."
The Brexit Secretary added the legal technicalities of Article 50 need to be addressed.
He said the current backstop arrangements under Article 50 are said to be legally temporary, contradicting what the Attorney General has said, which is that it could be indefinite.
The Prime Minister's statement comes ahead of a planned Commons debate on Thursday at the end of which MPs will still get to vote.
However, the vote is unlikely lead to a Government defeat.
On the subject of a permanent Customs Union membership she said it was "one thing" she and Jeremy Corbyn did not agree on.
"I would gently point out that the House has already voted against this," she told the Commons.
"It would allow an independent trade policy for the UK that would allow us to strike our own trade deals around the world, something the Labour party once supported."
Both the Prime Minister and Mr Corbyn have exchanged letters setting out their vision for Brexit.
Talks are continuing 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.
Guy Verhofstadt, Brexit Coordinator for the European Parliament, tweeted on Tuesday that despite meeting with the British politicians, he had yet heard of a proposal which could break the deadlock.
Mr Verhofstadt added that Mrs May should start cross-party negotiations.