"I'm disappointed with the amendment but actually the EU Withdrawal bill is making good progress through the House of Commons and we're on course to deliver on Brexit," May said as she arrived for an EU summit.
Hours before the summit May's own Conservative MPs rebelled on a vote on an amendment to the flagship bill that would give parliament the final say on a Brexit deal with Brussels.
"I'm looking forward to discussing that deep and special partnership for the future," May said.
"We're on course to deliver Brexit, we're on course to deliver on the vote of the British people."
Britain voted to leave the EU in a referendum in June 2016 and talks on its departure began a year later.
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