Boris Johnson has said he will press on “undaunted” with Brexit on 31 October, despite losing a crunch Commons vote.
The PM must now ask the EU for an extension to that deadline after MPs backed an amendment aimed at ruling out a no-deal Brexit, by 322 votes to 306.
But he told MPs: “I will not negotiate a delay with the EU and neither does the law compel me to do so.”
He vowed to bring in legislation on Monday to implement the deal he struck with Brussels this week.
MPs could also be given another vote on the deal on Monday, if Commons Speaker John Bercow allows it.
The Commons defeat is a major setback for the PM, who has repeatedly insisted that the UK will leave at the end of the month come what may.
Under the terms of the so-called Benn Act, passed last month by MPs determined to prevent a no-deal Brexit, he has until 2300 BST on Saturday to send a letter to the EU requesting an extension.
Mr Johnson said he was not “daunted or dismayed” by the Commons defeat and remained committed to taking Britain out by the end of the month on the basis of his “excellent deal”.