EU leaders have agreed to a Brexit delay 'until October 31' - diplomats
Video report by ITV News Europe Editor James Mates
EU leaders have agreed to a Brexit delay after Theresa May requested an extension to Article 50 beyond this Friday.
Diplomats have told Reuters the delay is "until October 31 with a review in June".
Donald Tusk has confirmed on Twitter that he will now meet Theresa May.
The prime minister asked for a delay to the end of June, with a break clause allowing the UK to leave as soon as Parliament has ratified her Withdrawal Agreement.
Mrs May told MPs last month that "as Prime Minister" she would not delay Brexit beyond the end of June.
But arriving in Brussels, she played down the significance of the comment, insisting that the important issue was securing the flexibility to leave early and avoid having to take part in European elections in May.
The prime minister also insisted leaving the EU in an "orderly way" is the best Brexit for the UK.
Mrs May said she "greatly regrets" the UK has not already left the EU.
Mrs May said: "What matters, I think, is I have asked for an extension to June 30 but what is important is that any extension enables us to leave at the point at which we ratify a Withdrawal Agreement.
"So we could leave on May 22 and start to build our brighter future."
ITV News Political Correspondent Paul Brand takes you behind the scenes of the EU summit in Brussels
The EU's chief negotiator Michel Barnier has said any delay to Brexit has to have a clear purpose.
He added: "Any extension has to be useful and serve a purpose. Our common purpose is to get the ratification of the Withdrawal Agreement".
"This Withdrawal Agreement is the only was to ensure an orderly withdrawal of the UK which is our common purpose."
French President Emmanuel Macron said: "for me, nothing is settled, and in particular no long extension".
He said he was "impatient" to hear what Mrs May had to say.
"We must understand today why this request, what is the political project which justifies it and what are the clear proposals?" he added.
Mr Macron said the leaders would need "a lot of calm, a lot of determination and a lot of sang-froid".
"It is 34 months since the British referendum, and the key for us is that we are able to pursue the European project in a coherent way," he added.
"I believe deeply that we are carrying out a European rebirth, and I don't want the subject of Brexit to get in the way of that."
He said it was important for EU leaders to respect the democratic decision of the British people, even if he did not agree with it.
Irish Taoiseach Leo Varadkar said he was open to either a short or long extension to Article 50.
On Mrs May's statement that she was not prepared to stay in the EU past June 30, he said: "Ultimately that decision lies with the House of Commons because the UK can leave before June 30, it can leave well before June 30 - it can leave in a matter of weeks.
"All that's required is for the House of Commons to ratify the agreement."
Mr Varadkar also it would be in the UK’s interests to remain within the European trading bloc.
Labour’s Jeremy Corbyn welcomed comments from Mr Varadkar suggesting he is ready to contemplate a role for the UK in helping decide EU trade policies if it remains in a customs union after Brexit.
Meanwhile Arlene Foster has accused Mrs May of trying to force people into backing her Brexit deal.
The Democratic Unionist leader described the PM's approach to Brexit as "weak" and damaging to the UK.
She made the comments ahead of her meeting with the EU's chief Brexit negotiator Michel Barnier.
Ms Foster will be joined by Northern Ireland MEP Diane Dodds as well as Conservative MPs Iain Duncan Smith and Owen Paterson at Thursday's meeting.
"This is a useful opportunity to once again set out why we oppose the Withdrawal Agreement and urge the EU's chief negotiator to acknowledge the concerns of those we represent in Northern Ireland by making the changes outlined by Parliament on 29 January.
"We cannot settle for a deal which would undermine the economic and constitutional integrity of the United Kingdom."
The DUP's 10 MPs had been supporting the minority Government in key decisions but have voted against Mrs May's proposed deal.
May and Merkel share a lighthearted moment as the EU leaders sit down for a working dinner to discuss an extension to Article 50
Mrs Merkel told German MPs the EU27 "may well" go for a longer delay, although the UK would be allowed to leave “very quickly” if Parliament approves a withdrawal deal.
However during Prime Minister's Questions earlier, Mrs May said a Conservative government will "make a success of whatever the situation is in relation to Brexit".
Addressing parliament, the Prime Minister repeated her opposition to a second referendum, but appeared to leave the option open for MPs to vote on one.
ITV News Political Editor Robert Peston on Mrs May's answer to a question on a second referendum
ITV News Political Correspondent Carl Dinnen says Mrs May's answer "leaves room" for another referendum
In response to a question from SNP Westminster leader Ian Blackford, Mrs May said: "My position on a second referendum and the government's position has not changed. The House has rejected a second referendum two times. When we come to a deal, we will have to ensure that legislation goes through this House.
"Of course, it may be there are those in this House who wish to press that issue as that legislation goes through. Though my position on this has not changed."