Iran and Japanese firm Inpex are likely to agree on a joint project to develop a big new Iranian oil field.
Azadegan field is one of the world's largest untapped oil reserves.
Any deal will no doubt raise eyebrows in the US which wants sanctions against Iran due to Tehran's nuclear ambitions.
While Japan is totally reliant upon oil imports, Iran is the world's fourth largest crude producer.
The Iranian government and Inpex first signed an outline agreement over the Azadegan field in 2004, but they subsequently failed to reach a final agreement due to a dispute over the exact financial structure of the deal.
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Japan, Iran to Jointly Explore Biggest Untapped Field
Azadegan field is one of the world's largest untapped oil reserves