Theresa May has been granted an extra two weeks to come up with a Brexit solution after talks with EU leaders.
The UK’s departure date had originally been set for 29 March.
If Mrs May can get her withdrawal deal through Parliament next week, that date will be pushed back to 22 May to give time to pass the necessary legislation.
If the prime minister can’t get the deal through, the UK will have to propose a way forward by 12 April for EU leaders to consider.
European Council President Donald Tusk said all Brexit options would remain open until then.
“The UK government will still have a choice between a deal, no deal, a long extension or revoking Article 50,” he said.
“The 12 April is a key date in terms of the UK deciding whether to hold European Parliament elections.
“If it has not decided to do so by then, the option of long extension will automatically become impossible.”
Mrs May ruled out revoking Article 50, which would cancel Brexit, and she also said “it would be wrong” to ask Britons to vote for candidates for the elections to the European Parliament, due to be held from 23-26 May, three years after they voted to leave the EU.
The UK’s departure date is still written in to law as next Friday, 29 March.