British Prime Minister Theresa May on Monday postponed a parliamentary vote on her Brexit deal to avoid a crushing defeat, saying she would return to Brussels for further talks - but the EU warned it would not reopen the agreement. In an emergency statement to the House of Commons, May conceded that the draft divorce agreement she struck with the European Union last month faced defeat by a "significant margin" of MPs on Tuesday.
She said she had "no doubt this deal is the right one" but promised to seek "further assurances" over a controversial backstop clause relating to Northern Ireland.
May said the date for a new vote depended on talks with other EU leaders, which officials said could begin with visits to European capitals starting on Tuesday.
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 ends its four-decade membership of the bloc with Brexit 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, while Tusk said the issue would be discussed on Thursday.
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 Monday she would relay concerns to EU leaders, but also warned the backstop was one of several "inescapable" compromises needed to get a deal.
"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?" she said.
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.
May spoke at the weekend to Tusk, German Chancellor Angela 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.
However, EU leaders have repeatedly warned they have no appetite to reopen a divorce deal forged through months of tortuous negotiations.
"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 on Monday.
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.
Opposition MPs shouted "resign" at May during her statement, and Labour leader Jeremy Corbyn said the decision to delay the vote was "desperate".
"The government has lost control of events and is in complete disarray," he said.
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 who argue her Brexit deal would leave Britain tied for years to the EU rules.
"This is not governing, it risks putting Jeremy Corbyn into government by failing to deliver Brexit," said leading Conservative rebel Jacob Rees-Mogg, who led a failed attempt to unseat May last month. "We cannot continue like this. The prime minister must either govern or quit."