British Prime Minister Theresa May on Monday postponed a parliamentary vote on her Brexit deal to avoid a crushing defeat, saying she would head to Europe for further talks -- but the EU warned it would not reopen the agreement.
In an emergency statement to the House of Commons, May conceded the draft divorce agreement she struck with the European Union last month faced defeat by a "significant margin" of MPs if held Tuesday.
She vowed "no doubt this deal is the right one" but would seek "further assurances" over a controversial backstop clause relating to Northern Ireland.
May said the date for a new vote depended on fresh talks with EU leaders, set to begin Tuesday in meetings with Dutch Prime Minister Mark Rutte in The Hague and then German Chancellor Angela Merkel in Berlin.
In response, EU President Donald Tusk called a special summit of the other 27 leaders to discuss Brexit on Thursday, at the start of a two-day Brussels meeting that May is due to attend.
But he warned: "We will not renegotiate the deal, including the backstop, but we are ready to discuss how to facilitate UK ratification."
The delay in signing off the deal, just months before Britain is set to end its four-decade membership of the bloc on March 29, sent the pound plunging to an 18-month low.
Sterling sank by more than 1.5 percent to $1.2527, the lowest since April 2017.
"This is yet another blow for companies desperate for clarity," said Carolyn Fairbairn, head of big business lobby the Confederation of British Industry.
Both May and Tusk also said they would look at stepping up preparations for the potentially catastrophic possibility that Britain leaves the EU without any new legal arrangements in place.
"For as long as we fail to agree a deal, the risk of an accidental no deal increases," May told MPs.
- Deliver Brexit? -
May faced a huge rebellion of her own Conservative MPs over the deal, primarily over the backstop clause designed to keep open Britain's border with Ireland.
The embattled leader said she would relay concerns to EU leaders, but also warned it was one of several "inescapable" compromises needed to get an agreement.
"If you take a step back it is clear that this House faces a much more fundamental question -- does this House want to deliver Brexit?" May added.
Earlier, the European Court of Justice gave hope to a small but growing number of MPs seeking a second referendum on Brexit, ruling that Britain was free to halt withdrawal from the bloc unilaterally.
- Cosmetic wording -
May spoke at the weekend to Tusk, Merkel and Irish Prime Minister Leo Varadkar, raising speculation they offered some hope of further concessions.
"We'll have to see what kind of assurances May wants. If the Brexit hardliners would be satisfied with some cosmetic wording, I don't know," a European diplomat said.
EU leaders have repeatedly warned they have no appetite to reopen a divorce deal forged through lengthy tortuous talks.
"It took over a year and a half to negotiate, it has the support of 28 governments, and it's not possible to re-open any aspect of that agreement without re-opening all aspects of it," Varadkar said.
He spoke by phone to Tusk Monday, when both reiterated the deal "is the best option and could not be renegotiated", according to his office.
"They also agreed that preparations for a 'no deal' outcome should intensify," it said.
Some EU officials have however mentioned the possibility of changes to the accompanying political declaration on future trade ties.
Charles Grant of the Centre for European Reform (CER) suggested May would only secure "very minor changes to her deal".
"The substance of the Irish backstop will be unaltered. So I very much doubt that parliament will vote for the deal, when it has the chance to do so," he said.
- 'Govern or quit' -
Many lawmakers reacted furiously to the delay, with Tory MP Mark Francois MP branding it "shameful".
"The government has gone away and hidden in the toilets," he said.
MPs successfully called for a three-hour emergency debate on the situation Tuesday.
Opposition lawmakers had shouted "resign" at the prime minister during her statement.
"The government has lost control of events and is in complete disarray," said opposition leader Jeremy Corbyn.
Labour had threatened to call a confidence motion in May if she lost Tuesday's vote, but pulled this after her Northern Irish allies pledged to support her.
But she still risks a challenge from within her own party from eurosceptics.
"We cannot continue like this," said leading Conservative rebel Jacob Rees-Mogg, who led a failed attempt to unseat May last month.
"The prime minister must either govern or quit."