U.N. nuclear chief urges immediate access to Iran site By Fredrik Dahl VIENNA (Reuters) - The U.N. nuclear watchdog chief pressed Iran on Monday to grant his inspectors immediate access to the Parchin military site, where they believe Tehran may have conducted explosives tests relevant to the development of nuclear weapons. Yukiya Amano, director general of the International Atomic Energy Agency, also said the IAEA and Iran had made no concrete progress in talks that began in January aimed at allaying concern about suspected atom bomb research in the Islamic state. Western powers may seize on his statement to a closed-door session of the IAEA's 35-nation governing board to strengthen their case for further increasing international pressure on Tehran, one of the world's largest oil producers. Amano made his comments one day after Israeli Prime Minister Benjamin Netanyahu said that Israel and the United States were in discussion on setting a "red line" for Iran's nuclear program. Israel, believed to be the only nuclear-armed state in the Middle East, sees the possibility of Iran developing an atomic bomb as a threat to its existence and has said it may use military means if diplomacy and sanctions fail. European Union heavyweights Britain, France and Germany called last week for new sanctions and Canada has unexpectedly severed ties with the country. The lack of concrete results despite months of discussions between the IAEA and Iran was "frustrating," Amano said. "We consider it essential for Iran to engage with us without further delay on the substance of our concerns," the veteran Japanese diplomat said, according to a copy if his speech. "Without Iran's full engagement, we will not be able to start the process to resolve all outstanding issues, including those concerning possible military dimensions to its nuclear program," Amano said. Iran's envoy to the IAEA, Ali Asghar Soltanieh, earlier told reporters that Tehran would "continue" to cooperate with the U.N. agency but that the Islamic Republic's national security must be taken into consideration. Iran says its nuclear program is entirely peaceful and is aimed at producing electricity, not making nuclear bombs. At the week-long IAEA board meeting, the United States and its Western allies want to isolate Iran further by adopting a resolution rebuking it for stonewalling the IAEA's investigation into its nuclear activities. But it is unclear whether China and Russia - who are also part of a group of six world powers trying to find a diplomatic solution to the long-running dispute - would agree to such a move, diplomats say. Beijing and Moscow have criticized unilateral Western punitive steps imposed against Iran. Russia last week starkly warned Israel and the United States against attacking Iran and said Moscow saw no evidence that Tehran's nuclear program was aimed at developing weapons. In contrast, the IAEA has voiced mounting concern of possible research and development work in Iran relevant for assembling a nuclear warhead. "Iran is not providing the necessary cooperation to enable us to ... conclude that all nuclear material in Iran is in peaceful activities," Amano told the IAEA board. He said "activities" which had taken place at the Parchin facility - a reference to suspected clean-up work there - would have an "adverse impact" on the IAEA's investigation, if and when it was allowed to go there. Iran has so far refused access. Citing satellite images, Western diplomats say Iran has for several months carried out apparent "sanitization" at Parchin to remove any evidence of illicit nuclear activity before possibly allowing the IAEA to visit. Iran told the agency in a letter last month that the allegation of nuclear-linked work at Parchin, located southeast of the capital Tehran, was "baseless," Amano said. "However, the activities observed further strengthen our assessment that it is necessary to have access to the location at Parchin without further delay in order to obtain the required clarifications," he said. Editing by Diana Abdallah