A team from the Vienna-based International Atomic Energy Agency (IAEA) went to the uranium enrichment plant at Natanz in central Iran on Thursday. On Friday they verified that no activities related to the production of uranium fuel were taking place.
"The IAEA went to Natanz and, among other things, verified the suspension," a Western diplomat familiar with the IAEA's investigation of Iran said.
The agency was expected to inform the IAEA's 35-member board of governors at next week's quarterly meeting that Iran had kept its promise about freezing sensitive work at Natanz and elsewhere, diplomats said.
Tehran has frozen its enrichment programme, which could produce fuel for nuclear power plants or weapons, under a November deal with France, Britain and Germany, which have offered Iran incentives to halt and dismantle the programme.
Inspectors complained of a
two-hour wait for access
The European trio shares Washington's suspicions that Iran is trying to develop nuclear weapons and is determined to prevent Tehran from mastering the science of enriching uranium.
Iran, which says its nuclear programme is for peaceful purposes only, has said the freeze at Natanz and elsewhere would last only until the end of July, when the European Union trio has promised to give Iran a detailed package of incentives.
However, the EU has said that resuming enrichment at Natanz, which is still under construction, would prompt it to back US calls to refer Iran to the UN Security Council for possible sanctions.
One diplomat with access to Iran's nuclear programme said the inspection team ran into problems when it tried to visit one facility at the 450-hectare (1110-acre) Natanz site because the Iranians refused to grant the inspectors access.
"The team that got to Natanz is having a lot of trouble there," a diplomat said on Thursday night.
"The Iranians are very strictly limiting their access."
The problem related to one specific facility and, after a delay of several hours, the situation was resolved and the team was let in, the diplomats said.
During the IAEA's two-year investigation of Iran's nuclear programme, members of the board of governors have criticised Iran for not showing full transparency or granting complete and immediate access to sites.
"They have visited wherever they have requested in Natanz facility and their inspections there are finished"
Iran Atomic Organisation
Diplomats said the brief delay raised concerns that Iran might have something to hide there, but an IAEA official said that, in general, the agency was getting all the access it needed.
"There are no problems with access at Natanz," an IAEA official said.
Mohammad Saeedi, deputy head of Iran's Atomic Energy Organisation, confirmed that IAEA inspectors had visited Natanz but denied there were access problems.
"They have visited wherever they have requested in Natanz facility and their inspections there are finished," he said.
Earlier this week, diplomats familiar with Iran's programme said Iran had stuck to the letter of its suspension agreement with the EU but had quietly continued construction work at Natanz to prepare for when they might want to resume enrichment.
Reporters taken on a tour of Natanz by government officials in March said it was more than 18m underground and surrounded by at least 10 anti-aircraft batteries - ostensibly in case of US or Israeli airstrikes.