British Prime Minister Theresa May on Monday won legally binding Brexit assurances from the European Union in a last-ditch attempt to persuade British lawmakers from voting against the agreement again, Reuters reported.

With the United Kingdom due to leave the EU on March 29, May met European Commission President Jean-Claude Juncker on Monday in France’s Strasbourg to discuss additional assurances. “Today we have secured legal changes,” May said in a late-night press conference. “Now is the time to come together to back this improved Brexit deal and to deliver on the instruction of the British people.”

The UK and the EU have differed over the terms of an Irish backstop, which is a “safety net” to preserve a border without customs and regulatory checks through a series of measures. British and European Union leaders had earlier committed to avoiding a “hard border” between Northern Ireland and the Republic of Ireland after Brexit. Pro-Brexit leaders in May’s Conservative Party insist that the backstop would make it impossible for Britain to leave.

May said the new documents, which involve a joint instrument, a joint statement and a unilateral declaration, would adequately address the backstop problem. MPs will vote on the new deal on Tuesday, the BBC reported. On January 15, the British parliament had voted to reject May’s deal by 230 votes, the biggest defeat for a government in modern British history.

May is expected to chair a Cabinet meeting on Tuesday morning before the motion is debated in the Commons and voting takes place in the evening.

Juncker, meanwhile, warned this was Britain’s last opportunity to seal the deal. “There will be no third chance,” he said. “There will be no further interpretations of the interpretations; no further assurances of the re-assurances – if the meaningful vote tomorrow fails.”

In a letter to EU Chairperson Donald Tusk, Juncker said Britain would have to elect its own EU lawmakers if it failed to leave by elections due in May. The European Parliament election will take place from May 23 to May 26. “It is this deal or Brexit might not happen at all,” said Juncker.

It’s unclear if the assurances would be enough to influence the 116 additional lawmakers May needs to reverse the earlier defeat. Labour leader Jeremy Corbyn called on MPs to reject the deal and said May’s “negotiations have failed”, The Guardian reported. “This evening’s agreement with the European Commission does not contain anything approaching the changes Theresa May promised parliament, and whipped her MPs to vote for,” he said.

The Democratic Unionist Party, which backs May’s party, said it would be “scrutinising the text line by line” before deciding whether to back the deal.