Prime Minister Theresa May will on Wednesday face a vote by MPs over her newly revised Brexit strategy, which allows for a possible request to delay Britain's EU departure if her divorce deal is not approved.
The embattled leader will ask lawmakers to approve a three-step plan set out Tuesday that would give her more time to attempt to rework a draft deal struck with the European Union more than three months ago.
Under the new plan, if she fails to come up with a deal that wins MPs' support by March 12, May would call a vote on a no-deal Brexit on March 13 and if that is voted down another vote on delaying on March 14.
In a piece for Wednesday's Daily Mail, May said her preference was for a deal allowing Brexit on March 29 and she urged parliament to vote in favour.
Parliament should "do its duty so our country can move forward," she wrote.
The prime minister, who reached an agreement with European leaders late last year but saw it overwhelmingly rejected by British lawmakers in January, had repeatedly ruled out delaying Brexit.
But her dramatic reversal on Tuesday came amid threats of mass resignations from her own ministers, who fear Britain leaving the EU without a deal on March 29.
The government published an updated assessment Tuesday of preparedness for such a scenario, which found a majority of businesses are not ready for a new trading regime.
It also warned that some food prices were likely to increase -- particularly for fresh fruit and vegetables --- and that this could "exacerbate, or create, shortages".
However, May's change in course has already angered Brexit hardliners in her own Conservative Party, with influential MP Jacob Rees-Mogg warning "any delay to Brexit is a plot to stop Brexit".
May is also set to face a series of votes on Wednesday from 1900 GMT on various amendments tabled by MPs, including cross-party moves to lock in her commitments made on Tuesday.
Many MPs are still anxious about the prospect of a no-deal departure, while Brexit hardliners want changes to the deal's so-called "backstop" clause to keep the Irish border open in all scenarios.
Rees-Mogg said MPs would not be able to block a no-deal, telling BBC radio that "if there is still no majority for the prime minister's deal... we are still faced with the same situation" after any delay.
He spelled out what changes May's deal would need to win his vote, saying he could back it "if there is a clear date that says the backstop ends".
An amendment put forward by Labour MP Yvette Cooper and Tory backbencher Oliver Letwin, seeks to bind May's commitments and help bring forward the "necessary legislation to change the exit date".
Meanwhile the main opposition Labour Party will table an amendment with five demands, including Britain remaining in a customs union with the EU after Brexit.
In a significant shift, the party's leader Jeremy Corbyn announced Monday that it would support a second referendum on the issue if, as is likely, he fails to get his demands adopted.
Cross-party supporters of another referendum on Brexit have also put forward an amendment to kick-start that process next month.
It is not expected to pass in the House of Commons, where a majority of MPs are still thought to be against another referendum.