BP Plc has had talks with Ghana's national oil company about a possible joint bid for Kosmos Energy's stake in the huge Jubilee oilfield off the coast of the country, Bloomberg said on Thursday, citing two people familiar with the matter.

BP has hired Goldman Sachs to advise on the deal, the report said.

Exxon Mobil agreed to buy the Jubilee stake from Kosmos in early October, according to three sources close to the matter. Kosmos is backed by private equity groups Blackstone Group and Warburg Pincus.

But state-run Ghana National Petroleum Corp has said the sale is illegal. A GNPC source said earlier this month that that the firm is interested in buying Kosmos Energy's stake itself, perhaps selling all or part of that stake later.

Moreover, a leading member of Ghana's ruling party said last week that the government does not approve of the Exxon deal.

BP declined to comment. Goldman Sachs could not be immediately reached for comment.

Kosmos owns the field with UK-based oil explorer Tullow Oil and Houston-based Anadarko Petroleum. It put its interest in the field on the market earlier this year.