A European official says British Prime Minister David Cameron and European Council President Donald Tusk will meet Sunday night to discuss the technicalities of the process needed if the U.K. decides to exit the bloc in the next couple of years.

Following an EU summit on Turkey and the refugee crisis on Sunday afternoon, Cameron and Tusk will meet for pre-arranged talks to work out details of a so-called Brexit.

The U.K. will hold a referendum on whether or not it should remain in the 28-nation EU by the end of 2017.

Cameron favors staying in provided he can secure a looser relationship between Britain and the bloc. He hopes to get into detailed negotiations on a deal at a December summit focused on Britain's EU membership.