The EU has agreed to delay Brexit until 31 January 2020 at the latest with the option for the UK to leave earlier if a deal is ratified, meaning the UK will not leave as planned on Thursday.
It comes as MPs prepare to vote on proposals by Boris Johnson for an early general election on 12 December.
Donald Tusk confirmed that the delay will be a "flextension"- meaning the UK could still leave before that date if a deal is ratified.
He tweeted: "The EU27 has agreed that it will accept the UK's request for a Brexit flextension until 31 January 2020. "The decision is expected to be formalised through a written procedure."
Boris Johnson has said in the past he would prefer to be "dead in a ditch" than miss the 31 October deadline. Something Guy Verhofstadt, the European parliament's lead Brexit spokesman, did not forget as he urged the UK not to waste this extension.
Relieved that finally no one died in a ditch. Whether the UK's democratic choice is revoke or an orderly withdraw, confirmed or not in a second referendum, the uncertainty of Brexit has gone on for far too long. This extra time must deliver a way forward.— Guy Verhofstadt (@guyverhofstadt) October 28, 2019
The prime minister had repeatedly said the UK would leave on 31 October deadline with or without a deal, but the law - known as the Benn Act - requires him to accept the EU's extension offer.
The president of the European Parliament, David Sassoli, said the extension was "positive", and "gives time for the UK to make clear what it wants".
The Liberal Democrats and Scottish National party have said they would back a general election on 9 December if no deal on 31 October was "taken off the table". Downing Street has let it be known that it is considering how to respond.
Labour continues to insist it will not back an election unless there are further assurances the UK will not crash out on 31 January.
Chris Cummings, chief executive of the Investment Association, has commented on the Brexit extension. He said: "It is crucial that politicians on all sides use this extra time to put their differences aside and work together on a solution that protects UK savers, our economy and our international competitiveness. The investment management industry has been preparing for all potential outcomes, whether the UK leaves with or without a deal.
"However, after over three years of negotiations, investment managers, UK savers and businesses are more than ever looking for much-needed certainty."
By agreeing the extension through a written procedure, most likely on Tuesday, EU leaders will avoid convening for a summit in Brussels.