European Union flags are seen outside the EU Commission headquarters in Brussels, prior to a meeting between Britain's Secretary of State for Exiting the EU Dominic Raab and EU's chief Brexit negotiator Michel Barnier, Belgium October 14, 2018. REUTERS/Francois Lenoir

BRUSSELS (Reuters) - British and EU negotiators called a pause in their talks on a Brexit deal on Sunday and will wait for the outcome of a summit mid-week before any resumption, four EU sources told Reuters.

“Despite constructive and intensive negotiations, several key issues remain unresolved,” one senior EU diplomat said. “No further negotiations are planned ahead of the European Council. The EU negotiator will brief the leaders who will then assess the progress so far.”

Others also said EU negotiator Michel Barnier would brief leaders of the 27 other member states when they meet for dinner in Brussels on Wednesday, on the eve of a regular EU meeting which British Prime Minister Theresa May will also attend.