VIENNA (AFP) - UN atomic watchdog chief Mohamed ElBaradei urged Iran on Monday to "unblock" a long-running nuclear standoff and expressed hope that a possible change in US policy towards Tehran may help break the deadlock. "I again urge Iran to implement all measures required to build confidence in the exclusively peaceful nature of its nuclear programme at the earliest possible date and to unblock this stalemated situation," ElBaradei said in his opening speech to the International Atomic Energy Agency's 35-member board of governors in Vienna. And he added: "I am hopeful that the apparent fresh approach by the international community to dialogue with Iran will give new impetus to the efforts to resolve this long-standing issue." While the Egyptian-born diplomat did not specifically mention the United States, he was clearly referring to President Barack Obama's signal that he is ready to talk with Iran directly. The US ambassador to the IAEA, Gregory Schulte, also addressed the first day of meeting, which wrapped up Monday and was slated to last until Thursday. As the first meeting since Obama's inauguration in January, "this is a moment of complex challenge for the IAEA, but also a moment of unparalleled opportunity," Schulte said. "The new administration intends to strengthen diplomatic efforts to address" the challenges of Syria and Iran, Schulte said. The two disputed dossiers were expected to be debated on Tuesday or Wednesday, diplomats said. Even after a six-year investigation, the IAEA has been unable to say once and for all whether Iran's controversial nuclear programme is entirely peaceful, as Tehran claims. Iranian foreign ministry spokesman Hassan Ghashghavi denied that Tehran was seeking to make a nuclear bomb. "All this talk is baseless," he said. "The agency expects Syria to provide additional information and supporting documentation about the past use and nature of the building at the Dair Alzour site," ElBaradei said. Meanwhile, Iran on Monday reiterated its denial that it is seeking to make a nuclear bomb, after top US military commander Admiral Mike Mullen alleged Tehran has enough fissile material to build such a weapon. "All this talk is baseless," foreign ministry spokesman Hassan Ghashghavi said at his weekly news conference. When asked if Iran had enough nuclear material to manufacture an atomic bomb Mullen told CNN on Sunday: "We think they do, quite frankly," the first time Washington has made such an assessment. But Ghashghavi on Monday insisted that Tehran is not working on making a bomb. "For that to be true, two things would have to happen... first, Iran has to exit the NPT (non-proliferation treaty) and second, it should be proved that Iran is seeking high-enriched uranium," he said. Ghashghavi said Tehran's nuclear programme is under the supervision of the UN watchdog, the International Atomic Energy Agency (IAEA). "Technically speaking there are IAEA cameras and the IAEA is testing the purity of Iranian material," he said. "Therefore, how can it be possible that with this level of supervision, low-enriched material can be turned into highly-enriched one?." The IAEA, in its report last month, said Tehran now has 1,010 kilograms (2,227 pounds) of low-enriched uranium hexafluoride (LEU) from its enrichment activities at a plant at Natanz. Some experts claim that is sufficient for a nuclear weapons breakout capability, which is defined as securing enough low-enriched uranium, used for nuclear fuel, to turn into highly enriched uranium (HEU) needed for nuclear weapons. While IAEA specialists put the amount needed for an atomic bomb at about 1,700 kilograms (3,748 pounds) of LEU, some analysts believe that smaller quantities might be enough. The West, led by the United States and Israel, suspect Iran's nuclear drive is aimed at making weapons but Tehran says the programme is solely aimed at generating electricity.