UPDATE 1-EU now sees Brexit unstoppable, aims to avert "fiasco"

EU summit chairman Donald Tusk said he had abandoned hope that Brexit might be stopped and said on Wednesday his priority was now to avert a "fiasco" in 50 days if Britain crashes out without a deal. Assuring Irish Prime Minister Leo Varadkar of the solidarity of all other member states as Dublin insists Britain give legal guarantees to avoid disrupting the Northern Ireland border, Tusk told a joint news conference in Brussels that he saw no force capable of blocking a "pro-Brexit" government and opposition.

As British Prime Minister Theresa May prepares to meet EU officials in Brussels on Thursday with a mandate from lawmakers to rework the withdrawal treaty she agreed with the Union in November, Tusk and Varadkar both echoed other European leaders in ruling out change to the text, including the Irish "backstop" -- the protocol which parliament roundly rejected last month. "I hope that tomorrow we will hear from Prime Minister May a realistic suggestion on how to end the impasse," Tusk said.

"I strongly believe that a common solution is possible." Tusk, the European Council president, said, however, that the EU must step up planning for Britain leaving on March 29 without having a legal agreement: "A sense of responsibility also tells us to prepare for a possible fiasco," he said.

(Editing by Jon Boyle)