LONDON - A Brexit deal has been agreed with the EU, Prime Minister Boris Johnson has said.

Mr Johnson tweeted: "We've got a great new deal that takes back control — now Parliament should get Brexit done on Saturday so we can move on to other priorities like the cost of living, the NHS, violent crime and our environment."

The announcement came as the PM was heading for a crunch EU summit in Brussels and follows days of intense negotiations.

After the deal was announced the Democratic Unionist Party said an earlier statement saying it could not yet back the Prime Minister's Brexit plans "still stands".

Jo Swinson, leader of the Liberal Democrats, said the PM's deal would be "bad for our economy" and said her party would continue to push for a second referendum.

"The fight to stop Brexit is far from over," she said.

"Boris Johnson's deal would be bad for our economy, bad for our public services, and bad for our environment.

"The next few days will set the direction of our country for generations, and I am more determined than ever to stop Brexit.

"When this deal comes to Parliament we will use every possible opportunity to give the public a 'people's vote' on the Brexit deal that includes the option to remain in the European Union."

Green Party MP Caroline Lucas tweeted: "PM is trying to railroad through a deal which will set course of UK for generations, with no parliamentary scrutiny, no independent analysis & no guarantee rights are protected. Parliament must be able to scrutinise fully & it must go back to people for #finalsay"

However, Boris Johnson has been dealt a major blow shortly before the crunch EU summit after Democratic Unionist Party leader Arlene Foster said she could not yet back his Brexit plans.

The Prime Minister is hoping to bring back a deal from the Brussels meeting of European leaders while winning the backing of the DUP, which also wields influence over some Tory Brexiteers.

But Ms Foster and her deputy, Nigel Dodds, released a joint statement hours before the summit was due to begin on Thursday, highlighting three major obstacles.