Cuban offshore oil drilling plans postponed again

* Summer drilling plans postponed until further notice

* Reasons for postponement unclear

By Marc Frank

HAVANA, July 7 (Reuters) - Cuba and a consortium of foreign oil companies have once again postponed plans to drill for oil in the island's still-untapped fields in the Gulf of Mexico, diplomatic and industry sources said this week.

Cuba had announced the consortium, led by Spain's Repsol-YPF (REP.MC: Quote, Profile, Research), would drill in June or July, but now it is uncertain when work will begin in the waters that Cuban oil experts say may contain 20 billion barrels of oil.

"The project has been postponed until a further date for more study," said a foreign oil industry source with direct knowledge of the plans.

"It is premature to say when drilling might begin, later this year or next," he added.

A European diplomat said he had first-hand knowledge that drilling was postponed at least until the end of 2009, if not into 2010.

Neither source wished to be identified. Cuban authorities were not immediately available for comment.