Iranian Oil Minister Kazem Vaziri-Hamaneh said that Tokyo was being given an extra 15 days to make its final decision on whether it sought to enter a pre-set deal to develop parts of the Azadegan oil field, southern Iran.
In 2004, Japan signed a two billion-dollar contract to develop Azadegan.
The Untied States opposes the Japanese venture.
Iran ranks second in oil production among the OPEC states, accounting for some 80 percent of the countrys export revenues.
