BRUSSELS (AP) — European Council President Donald Tusk says he hopes to hear suggestions from British Prime Minister Theresa May on how to keep the Irish border open following Brexit, after she rejected the EU's proposal.

May says the plan to keep Northern Ireland in the EU's customs union would "undermine the constitutional integrity of the U.K."

Tusk said Thursday that "in a few hours I will be asking in London whether the U.K. government has a better idea that would be as effective in preventing a hard border."

He said "no one has come up with anything wiser" than the option outlined in the EU's draft Brexit withdrawal text, which aims to keep people, goods, services and money flowing between the U.K.'s territory and EU member Ireland.