The unique authority for Iran\'s disputed nuclear program still rests with Supreme Leader Ayatollah Ali Khamenei after Hassan Rouhani was elected as the next president, a U.S. official said here on Wednesday. \"We\'ve got no reason to believe that it would change the fact that the unique authority for the nuclear weapons program in Iran rests with the supreme leader, and not with the office of the president,\" Thomas Countryman, U.S. assistant secretary for international security and nonproliferation, told reporters at the International Conference on Nuclear Security. However, he said the United States would still make efforts to pursue a diplomatic solution as long as the window for such a solution is still open, noting that greater transparency is needed to achieve such a solution. Rouhani said Iran\'s nuclear program would be more transparent, as is requested by some West states. However, the U.S. government doubted whether he has such a power to make the change. The West suspects the Islamic republic\'s nuclear program might have a military dimension, but Iranian officials insist that the nuclear activities of Iran are for civilian purposes. The International Atomic Energy Agency (IAEA) is seeking access to suspected Iranian military site. However, 10 rounds of talks between Tehran and the UN nuclear watchdog failed to reach any agreement for the investigation. Organized by the IAEA, the International Conference on Nuclear Security is being held in Vienna on July 1-5.