By Barbara Lewis and Paul Taylor
BRUSSELS (Reuters) - The British referendum on whether to leave the European Union has prompted Brussels officials to plan to postpone an EU summit scheduled on the same day, two diplomatic sources told Reuters.
One said the regular June meeting of the European Council, the heads of state and government of the 28 member states, would convene a week later, on June 30-July 1. Another said it was not clear when the event scheduled for June 23-24 would take place.
European Council officials had no immediate comment.
Last month, Prime Minister David Cameron scheduled the "Brexit" referendum for June 23 -- British elections are always on Thursdays -- meaning that the result would be known just as leaders were finishing dinner on the first day of their summit.
By delaying the Council, officials hope to ensure that the other leaders are able to take considered decisions in response to the referendum result. Opinion polls are tight as Cameron seeks to persuade Britons of the value of EU membership.
A vote to leave would strike a heavy blow at a Union already in crisis, depriving it of its second biggest economy. It would start a process of negotiation with London on the terms of a new relationship in trade and others areas likely to last for years.
(Writing by Alastair Macdonald; Editing by Catherine Evans)