Theresa May has indicated she may not bring her deal back to parliament for a third vote if there is not enough support for it.
In a letter to her fellow parliamentarians, she wrote: "If it appears that there is not sufficient support to bring the deal back next week, or the House rejects it again, we can ask for another extension before 12 April."
The prime minister set out four options available following the EU's acceptance of a delayed departure date.
The first option Mrs May sets out in her letter - to revoke Article 50 - would "betray the result of the referendum", she writes.
She explains how the second option, leaving the EU with no deal on 12 April, has already been rejected by MPs.
The third, pulling the next vote, could see her approach the EU for another extension which would see the UK remain in the EU during the European parliamentary elections.
The final option she offers is to simply carry on as planned: bring the vote next week, approve it, and leave on 22 May.
Sky News unpicks the new timetable agreed at a late-night summit in the Belgian capital
The prime minister also extended an offer to MPs to speak to her directly if they wish to in order to help them reach a decision.
Mrs May, who made a combative late-night speech on Wednesday, appeared to offer a conciliatory note to her colleagues.
She wrote: "I expressed my frustration with our failure to take a decision, but I know many of your are frustrated too.
"You have a difficult job to do and it was not my intention to make it any more difficult."
It comes as Number 10 is understood to be considering allowing parliament to vote on seven alternative options next week, amid growing fears that Theresa May will not get her Brexit plan through the House of Commons.
A senior minister in the government told Sky News that plans are being drawn up to give MPs a choice between revoking Article 50, a second referendum, the prime minister's deal, her deal plus a customs union, the deal plus a customs union and single market access, a standard free trade agreement, or a no-deal Brexit.
Meanwhile, a petition demanding Mrs May revokes Article 50 and cancels Brexit has passed 3.6 million signatures.
The petition says: "The government repeatedly claims exiting the EU is 'the will of the people'.
"We need to put a stop to this claim by proving the strength of public support now, for remaining in the EU. A People's Vote may not happen - so vote now."
The petition has had the highest rate of signatures on record - and at one point, it caused the official petitions website to crash.
Actors Hugh Grant and Jennifer Saunders promoted the petition on social media, as did physicist Brian Cox.