Prime Minister Theresa May has called on MPs to "hold their nerve" and come together behind an EU withdrawal deal which will deliver Brexit on time on March 29.
Addressing the House of Commons a fortnight after MPs voted for her to go back to Brussels and replace the controversial Irish border backstop, Mrs May acknowledged that she would need "some time" to hold talks with the EU.
She said that a planned Commons debate on Thursday will be on an amendable motion reaffirming the House's decision on January 29 that it supported the Government's efforts to find an alternative for the backstop and recognising that talks are ongoing.
Mrs May pledged to return to Parliament on February 26, if no deal has been secured before that time, to report back on progress and trigger a further MPs' vote the following day.
"We now all need to hold our nerve to get the changes this House requires and deliver Brexit on time," Mrs May told the Commons.
"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.
"And we can set this country on course for the bright future that every part of this United Kingdom deserves.
"That is this Government's mission. We shall not stint in our efforts to fulfill it."
Labour leader Jeremy Corbyn accused the PM 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 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.
"Now is not the time to stand idly by, now is the time to stand up and do the right thing: to rule out no deal and back Labour's alternative plan."