EU leaders have agreed in principle to extend Brexit until 31 January 2020 - meaning the UK will not leave as planned on Thursday.
EU Council President Donald Tusk said it was a "flextension" - meaning the UK could leave before the deadline if a deal was approved by Parliament.
It comes as MPs prepare to vote on proposals by Boris Johnson for an early general election on 12 December.
The SNP and Lib Dems have also proposed an election on 9 December.
The government has not ruled out getting behind that proposed date, if, as expected, it fails to get its preferred date through the Commons later.
The UK was due to leave the EU on Thursday, but Mr Johnson was required to request an extension after Parliament failed to agree on a Brexit deal.
Boris Johnson had repeatedly said the UK would leave on 31 October deadline "do or die", but the law - known as the Benn act - also requires him to accept the offer.
Mr Tusk will now seek the UK's formal agreement to the decision - before formalising the extension through a written procedure among the 27 other EU nations, which he hopes to conclude by Tuesday or Wednesday.
The BBC's assistant Political Editor Norman Smith said the decision saw a no-deal Brexit taken off the table - which will increase the pressure on MPs to decide on a general election.
MPs are due to vote on the prime minister's election call after 17:00 GMT.
Mr Johnson said if Parliament agreed to the vote, he would bring back his Withdrawal Agreement Bill for MPs to scrutinise.
The bill passed its first hurdle last week after MPs backed it at the second reading by a majority of 30.
But minutes later they voted against a timetable that would see it pass through Parliament in just three days, so the PM "paused" its progress.