VIENNA - A senior UN nuclear watchdog official said Iran needed to give his inspectors access to information, people and sites as he began a two-day meeting with Iranian officials on the Islamic state's disputed atomic activities on Monday.
Herman Nackaerts, deputy director general of the International Atomic Energy Agency, told reporters as he arrived at an Iranian diplomatic mission in Vienna that Iran should now engage on issues of substance with the IAEA.
The UN agency is investigating suspicions that Tehran may be seeking nuclear weapons capability, a charge it denies.
"The aim of our two days is to reach agreement on (an) approach to resolve all outstanding issues with Iran, in particular clarification of the possible military dimensions remains our priority," Nackaerts said.
Two previous rounds of talks in Tehran early this year failed to make any notable progress, especially on the IAEA's request for access to a military site where it believes nuclear weapons-relevant research may have taken place.
Since then, Iran and the six world powers have resumed wider diplomatic talks aimed at resolving the standoff over Tehran's atomic ambitions and they will meet again in Baghdad on May 23.
Western diplomats will be watching this week's discussions in Vienna for any sign that Iran is now ready to address the IAEA's concerns about its nuclear work, saying this would send a positive message ahead of the Baghdad talks.
"We are here to continue our dialogue with Iran in a positive spirit," said Nackaerts, who heads a team of senior IAEA officials in the meeting at the Iranian diplomatic mission.
"It is important now that we can engage on the substance of these issues and that Iran let us access to people, documents, information and sites," he said.
Iran and the powers involved in nuclear diplomacy - the United States, Russia, China, Britain, France and Germany - revived negotiations in Istanbul last month after a 15-month hiatus and both sides say they hope for progress in Baghdad.
The resumption of diplomacy offers a chance to defuse soaring tension that has raised fear of a new Middle East war.
Israel - widely believed to hold the Middle East's only nuclear arsenal - and the United States have not ruled out military action to prevent Iran from obtaining atomic bombs if negotiations fail to achieve this objective peacefully.
Two previous meetings between Iran and the IAEA in Tehran early this year failed to make any notable progress.
The UN agency's document published in November lent independent weight to Western allegations about Tehran's nuclear agenda and helped pave the ground for a significant ratcheting up of US and European sanctions to block its oil exports.
One finding in the report was information that Iran in 2000 had built a large containment chamber at Parchin - a military complex southeast of Tehran - in which to conduct high-explosives tests that the IAEA said are "strong indicators of possible (nuclear) weapon development".
Iran has rejected the accusations as fabricated but so far has not granted repeated requests by the UN agency to visit the place. IAEA head Yukiya Amano says the issue is a "priority" for his team of senior officials in this week's discussions.