"We expect to visit Parchin within the next days or a few weeks," ElBaradei told AFP, referring to the huge complex 30 kilometres (19 miles) southeast of Tehran.

The International Atomic Energy Agency (IAEA) headed by ElBaradei has been seeking access to Parchin since July. Tehran has strongly denied carrying out any nuclear-related work at the site.

A senior US official told AFP that the Iranians may be working on testing "high-explosive shaped charges with an inert core of depleted uranium" at Parchin as a sort of dry test for how a bomb with fissile material would work.

Iran maintains that its nuclear program is strictly civilian and peaceful and that it is not developing atomic weapons.

But the United States wants the IAEA to take Iran to the UN Security Council for possible sanctions for what Washington says is a covert nuclear weapons program.

ElBaradei says the "jury is still out" on whether Tehran's program is peaceful or not.

Parchin is an example of a so-called "transparency visit," where the IAEA is going beyond its mandate under the nuclear Non-Proliferation Treatyto check to see if nuclear materials have been diverted away from peaceful use.

There could very well be no nuclear material at Parchin, since the concern there is of weapons simulation testing. The other problem is that Parchin is a military site, to which access is more difficult.

Still, ElBaradei said that where there is suspicion of weapons work, there is also a suspicion of nuclear materials, the "choking point" for development of weapons.

"If you do not have nuclear materials, you do not have a nuclear weapon," he said.

ElBaradei also said Iran is so far honoring its pledge to suspend uranium enrichment, and should finish processing the raw uranium it was allowed to do by February.

Iran is making a uranium powder that is a key first step in the enrichment process that can make nuclear weapons but it is not in violation of a nuclear freeze agreed with the European Union.

Iran and the EU embarked in December on negotiations towards a long-term agreement to give Tehran trade, technology and security aid and guarantees in return for it taking steps, such as suspending enrichment, to reassure the international community that its nuclear program is strictly peaceful.

In other comments, ElBaradei warned the United States against spying on the IAEA, saying it would be a blow to "multilateralism and the United Nations system as we know it."

The Washington Post reported in December that US President George W. Bush's administration had listened in on phone calls between ElBaradei and Iranian diplomats, seeking ammunition to oust him as head of the IAEA.

The United States wants ElBaradei to be replaced at the Vienna-based agency believing he is not being tough enough on Iran, diplomats said.

ElBaradei said he had only read the press reports and knew no more about the reported eavesdroping but "if you tamper with our independence, you really tamper with the whole fabric of multilaterialism and the United Nations system as we know it."

Questioned about reports that the IAEA is looking into exploratory moves by Egypt on making nuclear fuel that could be used for atomic bombs, ElBaradei said people should be careful to distinguish between what can be technical failures to comply with international safeguards and actual weapons programs.

"Should we discover at any time that there is a proliferation concern or implications of a weapons program, we will obviously promptly report this to the board," he said, referring to the IAEA's board of governors while refusing to comment specifically on Egypt.

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