UPDATE 1-France confident of a Brexit deal, though not by Wednesday night

"We remain confident in the idea a deal can be reached, though probably not by Wednesday night," the official briefed journalists.

France is confident a Brexit deal can be struck, though unlikely by Wednesday night when EU leaders meet in Brussels, with the Irish border among the trickiest of issues to resolve, an official in the French presidency said on Tuesday.

"We remain confident in the idea a deal can be reached, though probably not by Wednesday night," the official briefed journalists.

"We already said in Salzburg that we were at a moment of truth, time is running out."

The official said an extension of the article-50 negotiation period beyond March 29, 2019, was legally possible but "not desirable". Such an extension was not being worked on by either EU or British negotiators, the official added.

The official said France, which has taken a tough stance on preserving a united European front, expected the 27 EU leaders to send a message of both "openness" and "urgency" to Britain on Wednesday.

At the last summit in Austria, Macron called British Prime Minister Theresa May's so-called Chequers plan "unacceptable" and denounced pro-Brexit campaigners as "liars" who sold Brexit to the public as an easy process.

(With inputs from agencies.)