That appears to have been resolved after a long night of negotiations, when according to Reuters reports, Spain reached a deal with the EU on Gibraltar, clearing the way for the EU summit on Sunday to approve a Brexit deal with British Prime Minister Theresa May.

"Negotiations went on through the night with Spain and Britain. In a telephone conversation just now (European Council President Donald) Tusk and (Spanish Prime Minister Pedro) Sanchez reached an agreement on Gibraltar," the source said. "The summit will go ahead.

"Separately, Bloomberg reports that according to draft agreement it has seen, "after the United Kingdom leaves the Union, Gibraltar will not be included in the territorial scope of the agreements to be concluded between the Union and the United Kingdom," the EU leaders will say in statement on Sunday.