Adds Chevron becoming operator, more time to evaluate seimic

ATHENS, May 28 (Reuters) - U.S. oil major Chevron CVX.N has filed an official request to take over a 70% stake from Greece's Helleniq Energy HEPr.AT in an offshore block southwest of Greece, the Greek energy ministry said on Thursday, in a move that would further expand the United States' presence in the Mediterranean.

Once approved, Chevron will become the operator and lead the search for gas in Block 2 in the southwest of the Ionian Sea, with Helleniq retaining 30%, the ministry said in a statement.

Greece is considering giving Chevron and Helleniq more time to evaluate seismic data that have been completed for the area before they decide on any exploratory drilling there, the ministry added.