Hopes for defusing the Iranian nuclear crisis were thwarted Wednesday when the International Atomic Energy Agency (IAEA) said Iran did not agree to clear up nuclear weapons allegations and refused access to a site during a visit by senior agency officials.

"It is disappointing that Iran did not accept our request to visit Parchin during the first or second meetings," said IAEA Director General Yukiya Amano, referring to a military site where a simulated nuclear warhead was allegedly tested.

"We engaged in a constructive spirit, but no agreement was reached," he said.

His statement came hours before a senior team of IAEA officials was expected to return from Tehran to Vienna after a second round of talks with Iranian nuclear officials that was accompanied by rising tensions between Iran and Israel.

The world's nuclear watchdog said it had made intensive efforts to agree on a document that outlines how Iran would answer outstanding questions about its suspect nuclear activities and give access to documents, officials and locations.
"Unfortunately, agreement was not reached on this document," the IAEA said.

Iranian Foreign Affairs Ministry spokesman Ramin Mehmanparast said Tuesday that the senior IAEA team had not come to inspect sites but to hold talks.

However, a Vienna-based diplomat closely following the issue said the delegation had in fact wanted to visit Parchin, 30 kilometers south-east of Tehran, during two trips late last month and this week in addition to asking for access in the future.

Since 2008, Iran has refused to answer the IAEA's questions about alleged nuclear weapons research and development projects. The IAEA has made clear that these activities appear to cover all key stages of developing and testing components for such arms, judging from its own information gathering and from intelligence material.

Iranian leaders said the intelligence findings were fabricated and it pursues nuclear technology only for electricity and other civilian uses.

Iran on Monday began a military exercise to prepare the defense of its nuclear sites amid growing tensions with Israel. The country has not ruled out the possibility of military strikes to prevent Iran from developing a nuclear bomb.

The United States has been trying to persuade Israel not to attack Iran's nuclear facilities, according to recent media reports.