South Korea's national oil company is interested in buying a stake in Ghana's giant Jubilee oil field, the Korean firm and Ghana's state oil agency said on Friday.

"They have expressed interest in everything -- exploration, production and all the potential downstream activities," said Thomas Manu, director of production at Ghana National Petroleum Corporation (GNPC).

Discussions between the two parties were at a preliminary stage, he told Reuters after a delegation from Korea met Ghanaian officials.

"Korea National Oil (Corp) is interested in participating in exploration and also in Kosmos' assets," said KNOC President and Chief Executive Young-won Kang.

GNPC is in protracted talks to buy the Jubilee stake owned by privately-held Kosmos Energy. A Ghanaian government source said in February the government wants to block a reported deal for Kosmos to sell its interest in the field to Exxon Mobil (XOM.N) for $4 billion.

"(The Koreans) have expressed interest in buying a portion of it if we acquire it," Manu said.

Jubilee, forecast to begin producing later this year, has recoverable reserves of 800 million barrels, Ghana's Energy Minister Jospeh Oteng-Adjei said last month.