Blackstone and Warburg Pincus-backed Kosmos Energy said it has called off the sale of its Ghana oil assets to Exxon Mobil, dealing a blow to the US oil group's drive to tap a major new oil region in west Africa.

Closely-held Kosmos said it was now focused on developing the huge Jubilee oil field and appraising new offshore discoveries with partners such as Anadarko Petroleum and Tullow Oil.