Brexit talks: Macron says nothing is settled as Merkel pushes for short delay

European Council President Donald Tusk, left, speaks with British Prime Minister Theresa May, centre right, German Chancellor Angela Merkel and Luxembourg's Prime Minister Xavier Bettel. Photo / AP

Emmanuel Macron has warned there can be no guarantee that the EU will grant Theresa May another extension to Article 50 as he arrived in Brussels for the EU leaders' summit.

"For me, nothing is settled, and in particular no long extension ... we must understand today why this request, what is the political project which justifies it and what are the clear proposals?" the French President said.

"I believe deeply that we are carrying out a European rebirth, and I don't want the subject of Brexit to get in the way of that."

It came as Angela Merkel threw the British Prime Minister a lifeline by telling German MPs any Brexit extension should be "as short as possible" ahead of the summit this morning NZT.

The German Chancellor has revived hopes that the Prime Minister could secure a shorter Brexit delay, but added that it should be "long enough to create calm, so we don't have to meet every two weeks".

May has requested that Article 50 be extended until June 30.

However, there is a growing expectation in Westminster that EU leaders will back Donald Tusk's 'flextension' plan for a year-long delay, with the option for the UK to leave earlier if Parliament ratifies the Brexit deal in good time.

Macron has put forward an alternative plan which would see the UK relegated to an "intermediate member state" - shut out of major decisions and required to undergo a membership review every three months.

But in a boost for May, Merkel told the Bundestag: "I will support - and see if there's broad majority for - an extension of several months, but not far beyond that so that when the UK decides, an exit can proceed successfully.

"The extension should be as short as possible, but it should give us a certain amount of calm so that we don't have to return to this issue every two weeks."