Shell will sign a memorandum of understanding with the ministry regarding the South Azadegan and Yadavaran oil fields, near the Iraqi border, and the Kish gas deposit in the Persian Gulf, the official said, asking not to be identified because he isn't authorized to speak to the media.

Talks are ongoing with Total for other fields, but no agreement is expected imminently, the official said. He had earlier said Total and Shell would sign agreements on Wednesday.

Shell's agreement will be to form working groups to assess the potential for future investment, not to develop fields, according to a person with knowledge of the matter. Representatives of Total and Shell declined to comment.