NEW DELHI—State-owned Ghana National Petroleum Corp. said Monday it has made a $5 billion joint bid with China’s Cnooc Ltd. to buy Kosmos Energy’s assets in the African nation, including its stake in the Jubilee oil field.

However, Dallas-based Kosmos doesn’t want to exit the Jubilee project, according to GNPC’s chief geophysicist, Gabriel Q.A. Osatey, who spoke with reporters on the sidelines of the Petrotech energy conference in New Delhi.

“Kosmos has now decided to remain. That is for sure,” Mr. Osatey said. “GNPC wanted to buy it” but now cannot do so, he said. Kosmos declined to comment.

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