The president of the European Council on Monday called a meeting of EU leaders to discuss Brexit, but warned they would not renegotiate the withdrawal deal.
After British Prime Minister Theresa May postponed a parliamentary vote to approve the deal, EU chief Donald Tusk said the leaders would meet on Thursday.
"We will not renegotiate the deal, including the backstop, but we are ready to discuss how to facilitate UK ratification," he wrote.
"As time is running out, we will also discuss our preparedness for a no-deal scenario." A spokesman for Tusk said the timing of the meeting, which will come on the first day of a planned European Council summit, was still to be determined.
"Based on Prime Minister May's decision to defer the vote, President Tusk has decided to call European Council, Article 50, on Thursday," he said.
"There will be no renegotiation of the November 25 agreement but the EU27 stands ready to discuss how to facilitate UK ratification," the spokesman said.
"We are in contact with the UK on how it wants to proceed," he said, adding that Tusk is consulting the other 27 leaders of the remaining EU member states.