Iran, under heavy US-led pressure to curb its nuclear program, has opened a high-security military site to UN nuclear inspectors who also met senior personnel at the facility, an Iranian official said Sunday. Foreign Ministry spokesman Hamid Reza Asefi said the approval was given to the inspectors after they requested to visit the Parchin military site, about 30 kilometers (20 miles) southeast of Tehran, which US officials claim may be part of Iran's nuclear arms research program. "This was not the first time. They had visited Parchin before. This time they asked to visit other areas of the site," Asefi told reporters during his weekly press conference. "They talked with our friends this time. What they have done in Iran has been in the framework of the NPT (nuclear nonproliferation treaty) and safeguards," he said without elaborating. It was unclear when the inspectors visited Parchin, but it took place after their arrival in Iran on Oct. 28 for a weeklong visit. The visit followed repeated efforts by the UN's nuclear watchdog, the International Atomic Energy Agency, to make a return visit to the site after a previous inspection in January. Inspectors wanted to conduct further checks of radioactivity in buildings and areas within the sprawling military complex. The January visit revealed no such traces. The United States and other Western nations suspect experiments linked to Iran's nuclear program are being conducted at the Parchin complex. Iran denies claims that is nuclear program is aimed at building nuclear weapons. With the next IAEA board meeting only weeks away, Iran is under increasing pressure to show it is cooperating with a UN probe of suspected clandestine nuclear activities as it tries to derail a US-backed European push to report it to the Security Council.