U.N. nuclear agency expresses 'serious concern' about Iran nuke activity September 13, 2012 -- Updated 2109 GMT (0509 HKT) The resolution expresses concern about Iran's nuclear activity And it calls on Tehran to cooperate with international nuclear regulators The International Atomic Energy Agency will hold its general conference in Vienna next week (CNN) -- The United Nations' nuclear watchdog organization overwhelmingly passed a resolution Thursday stressing concern about Iran's continued nuclear activity while simultaneously urging Tehran to cooperate with international nuclear regulators. At the International Atomic Energy Agency Board of Governors meeting in Vienna, the vast majority of voting nations agreed with the draft resolution designed by the so-called P5+1: the United States, France, Russia, China, Britain -- the five permanent members of the U.N. Security Council -- and Germany. In the resolution pressuring Iran to comply with the Nuclear Nonproliferation Treaty, the IAEA notes that while dialogue between Iran and the agency has "intensified," the two sides have been unable to agree on how to proceed. The resolution says that in the meantime, Iran has not granted regulators access to certain sites, including Parchin, a military site where some observers suspect Iran has been demolishing a facility dedicated to nuclear weapons research. In a statement, the United States reiterated its call for Iran to grant the IAEA immediate access to the Parchin site, asking, "If Iran has nothing to hide there, why did it begin altering the site as soon as the IAEA asked to visit?" The IAEA resolution adds that the agency's director general believes Iran's actions will significantly hamper regulators' ability to effectively verify what has been going on at the sites in question. The resolution stresses the Security Council's overall goal of a peaceful, negotiated long-term solution, which the IAEA says could best be achieved through a diplomatic process that restores international confidence that Iran is using its nuclear technology for exclusively peaceful uses. However, the U.S. statement questioned whether that's a realistic expectation. "It is clear by Iran's dismissal of the Agency's concerns that, despite Iran's repeated pledges of cooperation and the reiteration in the November 2011 Board of Governors resolution of Iran's obligation to do so, Iran has no intention of responding in good faith," read part of the U.S. statement. The IAEA's 56th General Conference will meet in Vienna next week, from September 17 through September 21.