Updated 3:05 p.m.
(CBS/AP) VIENNA - Six world powers called on Iran on Thursday to let inspectors from the International Atomic Energy Agency visit the Parchin military site where the U.N. nuclear watchdog says work relevant to developing nuclear weapons may have taken place.
The joint call demonstrated unusual unity and points to growing concern among the nations over the Iranian crisis.
IAEA Director General Yukiya Amano said on Thursday that Iran has not formally contacted the IAEA about any inspector access to Parchin, a day after Iranian media suggested such a visit could happen.
The six IAEA member nations - the United States, Russia, China, Britain, France and Germany - urged Iran to answer questions about whether it is working on nuclear weapons, but stressed that diplomacy was the way forward.
This comes amid reports that Tehran might be cleaning it of evidence of nuclear arms-related experiments, a request echoed by other speakers at the 35-nation IAEA board meeting.
"We've had concerns about Parchin that's why we wanted the IAEA to get in there," said U.S. State Department spokeswoman Victoria Nuland. "The Iranians were supposed to allow that a couple of weeks ago. They didn't... we are all concerned."
Meanwhile, Iran's Supreme Leader Ayatollah Ali Khamenei Reuters reported.who recently said he saw a "window of opportunity" to use diplomacy to resolve the nuclear dispute. But Khamenei said Washington's simultaneous moves to "bring the Iranian people to their knees" with harsh sanctions were driven by delusion,
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While also stressing that diplomacy was the key to resolving tensions over Iran's nuclear program, a European Union statement was stronger than that from the six powers, noting "regret" of Iran's lack of response to international concern.
The EU's foreign policy chief said on Tuesday the six powers had accepted Iran's offer to revive the stalled talks. The Islamic Republic's chief nuclear negotiator Saeed Jalili last month promised to float "new initiatives" at the talks, whose venue and date are not yet decided.
But Iran's ambassador to France, Ali Ahani, said on Thursday its "inalienable" right to enrich uranium would not be on the table.
Concerns about Parchin are high. Diplomats who spoke to The Associated Press on Wednesday based their assessment on satellite images of the Iranian military facility they said appeared to show trucks and earth-moving vehicles, indicating an attempted cleanup of radioactive traces.
Two of six diplomats said their information reveals that Iran had experimented with a test version of a neutron trigger at the site used to set of a nuclear blast - information not previously made public.
The IAEA has already identified Parchin as the location of suspected nuclear weapons-related testing. In a November report, it said it appeared to be the site of experiments with conventional high explosives meant to initiate a nuclear chain reaction.
Iran vehemently denies allegations that it conducted any research and development into atomic weapons and says the totality of its nuclear activities are meant purely to generate power or for research.
IAEA expert teams trying to probe the suspicions of secret weapons work by Iran tried, and failed, twice in recent weeks to get Iranian permission to visit Parchin.
Tehran said on Monday that such a visit would be granted. But it said that a comprehensive agreement outlining conditions of such an inspection must first be agreed on - a move dismissed by a senior international official familiar with the issue as a delaying tactic.
He requested anonymity because his organization does not authorize him to speak publicly on confidential IAEA matters.
The EU statement was sprinkled with diplomatic code words meant to convey strong criticism of Iran's defiance of international demands that it lower tensions levels by compromising on its nuclear activities.
"We deeply regret" Iran's lack of efforts to dispel international suspicions, said the statement, urging it "to enter without delay" into a dialogue with the agency that leads quickly to diminishing fears of a secret nuclear-weapons agenda on the part of Tehran.
German Foreign Minister Guido Westerwelle was even more direct. He said Germany and the five other world powers trying to engage Tehran on its nuclear program were sending "a clear message to Iran to finally end its non-cooperation and to clear up all the justified concerns about the purpose of its atom program transparently and logically."