The government of Ghana has blocked the estimated $4bn sale of a stake in its Jubilee oil field, foiling months of talks between potential buyer Exxon Mobil Corp and the stake’s owner Kosmos Energy LLC, according to US media reports.

A Ghanaian official said state-run Ghana National Petroleum Corp would be the only entity allowed to buy Kosmos’ stake in the field, according to a report in the The Wall Street Journal.

Exxon spokesman Patrick McGinn said the company does not “comment on the details of commercial discussions or opportunities”, adding only that it “routinely evaluates potential development opportunities around the world”, reports Reuters.

Officials at the Ghanaian government could not immediately be reached for comment, the news agency reports.