EU-27 unimpressed by May, offer little on Brexit

However, it did not offer to look into further assurances, as an earlier leaked draft had said.

"Our UK friends need to say what they want, rather than asking what we want. We would like in a few weeks for our UK friends to set out their expectations because this debate is sometimes nebulous and vague and I would like clarifications," EU commission president Jean-Claude Juncker told reporters after the meeting.

May saw the 27 leaders a day after having survived a leadership challenge by her Conservative Party.

She sought to secure political, and possibly legal, assurances that the backstop arrangement, which keeps the UK in the EU's customs union until a future relationship is agreed, was provisional and temporary in nature.

May had already postponed the vote in the UK parliament on the Brexit deal once earlier this week, with Brexiteers fearing the backstop arrangement could last for decades.

According to the Brexit deal, the backstop would only kick in after the transition period at the end of 2020 if there was no agreement on the future relationship in place by then.

Sources said that during Thursday's discussions, the British prime minister failed to offer anything concrete on what would help her to get the agreement through her rebellious parliament, with German chancellor Angela Merkel interrupting her several times to ask May what she really wanted.

According to a source, May had asked for a legally binding provision that the backstop would be temporary, but EU leaders pointed out that it was already in the agreement.

In Thursday's statement, the EU-27 reiterated that the backstop was only to be used "unless and until it is superseded by a subsequent agreement that ensures that a hard border is avoided."

May also pushed for an end-date for the backstop to be 2021, but EU leaders pointed out that the backstop cannot have a prefixed end date, because that kills its purpose - to act as a bridge between the transition and a negotiated future deal.

"You cannot put a fixed date in writing. What would happen if you have a fixed date and there is no new relationship? Then you would still have a hard border in Ireland and would still work against the Good Friday agreement," Dutch prime minister Mark Rutte said after the meeting, referring to the 1998 peace deal that ended the sectarian conflict on the island of Ireland.

"This is not what the European Union was originating from, which is to prevent war in Europe. This is also a UK wish, this is a joint red line," he added.

Rutte spoke about the lack of trust in the UK that could possibly undermine future talks with Britain.

"We were all a bit struck back by the fact that this has become such a big issue in the debate in the UK parliament, and that there is so much mistrust behind it," he added, saying the backstop was not in the EU's interest either.

Sources said that despite the goodwill in the room, EU leaders were left wondering if May had a strategy on how to get the votes she needs in the British parliament.

Danish prime minister Lars Lokke Rasmussen said on his way out of the summit that the UK should have gotten a national compromise between political parties before negotiating with the EU to make sure a deal would go through the parliament.

In a sign of an increased likeliness of a no-deal Brexit, Juncker said the EU commission will publish next week further measures on preparing for the UK crashing out of the bloc.