British Prime Minister Theresa May says she has secured what she called "legally binding" changes to her Brexit deal with after her meeting with European Commission President Jean-Claude Juncker.
Their last ditch talks in Strasbourg came on the eve of a crucial parliamentary vote in London on Tuesday.
However, Juncker warned if the deal was voted down there was "no third chance".
The so-called Irish backstop remains a key sticking point.
Many Brexiteers fear an open Irish border would subject the UK to EU customs rules permanently.
The opposition Labour Party questioned whether any changes had actually been made and urged MPs to vote against the deal in Tuesday's vote