Brexit secretary Dominic Raab has rushed to Brussels for crunch talks with Michel Barnier.
Mr Raab is meeting Mr Barnier, the EU’s chief negotiator, for negotiations as the government desperately tries to secure a Brexit deal.
The surprise talks come before a key meeting of EU leaders on Wednesday, with the government admitting there are "big issues still to resolve".
A Department for Exiting the European Union spokesman said: "With several big issues still to resolve, including the Northern Ireland backstop, it was jointly agreed that face-to-face talks were necessary ahead of this week's October European Council."
Meanwhile, Reuters reported ambassadors for all EU member states, excluding Britain, were summoned to a meeting on Brexit at the same time as Mr Raab's talks were taking place.
It follows a weekend in which Prime Minister Theresa May faced fresh attacks from her former Cabinet colleagues over Brexit, as well as speculation over further resignations.
On Sunday, Mr Raab's predecessor David Davis called for Cabinet mutiny against Ms May’s Brexit plan, which he described as “completely unacceptable”.
But Tory vice-chairman James Cleverly urged Cabinet ministers to use their position to influence Brexit policy rather than resign. "I would suggest that's a much more constructive and helpful way of influencing the direction of the negotiations with the EU," he told Sophy Ridge on Sunday.
