Exxon Mobil and CNOOC Ltd filed cases before the International Chamber of Commerce last month, seeking to claim a right to a first refusal over any sale of Hess' 30% stake in the giant Stabroek offshore oil block in Guyana. Hess confirmed the case could drag on until year-end and ultimately block the deal. Separately, Hess has reaffirmed that it does not anticipate the need for regulatory approval from the Guyana government for this deal. (Reuters - Reporting by Sabrina Valle; Editing by Leslie Adler)