A154Japan is tackling the issue by independently developing oil fields in the Middle East and other regions using Japanese capital, as well as by developing natural gas and coal. The Arabian Oil Company, Ltd., a Japanese oil field developer, gained explo-ration rights (concession rights) for the Khafji oilfield from the Saudi Arabian government and commenced operations there, but the exploration rights expired at the end of February 2000. Negotiations with the Saudi Arabian government to extend these important exploration rights were not successful. So Arabian Oil put all its efforts into extending the exploration rights for the Kuwaiti half of the oil field, which were valid until January 2003. By March 2002, Arabian Oil and the government of Kuwait had reached an agreement that operations in the Kuwaiti part of the field would continue. Japan has been negotiating with Iran for commercial production of the Azadegan oilfield which has the largest proven oil reserves in the Middle East, estimated at 26 billion barrels. The United States, which strongly objects to Iran's nuclear development program, is demanding restraint on all major investments in Iran. In October 2006, the Japanese oil exploration company INPEX Corp. announced that it had reached agreement with the government of Iran to massively reduce its rights in the Azadegan oilfield from 75% to 10%.