Iran has invited several ambassadors accredited to the International Atomic Energy Agency in Vienna to tour its nuclear facilities, a senior European diplomat in Brussels told Reuters on Monday.

The move comes just weeks before a second round of nuclear talks with Britain, China, France, Germany, Russia and the US, and could signal an effort by Tehran to show it is serious about the talks.

'At a minimum, it sounds as if Iran is trying to put a positive face on the discussions,' said Columbia University Iran expert Gary Sick, a former senior US National Security Council official.

The European diplomat, who declined to be named, said the invitations had been made in a letter to the ambassadors. He did not say which countries had been invited.

Major powers want Iran to halt its uranium enrichment programme, which many of them suspect is a cover for an effort to build a nuclear arsenal. Iran says it has the right to enrich uranium for civilian use and does not want atomic weapons.

After more than a year without negotiations, Iran held talks last month in Geneva with the five permanent members of the UN Security Council plus Germany. A second round of talks is due later this month in Turkey.

After years of successfully exploiting divisions within the UN Security Council to sidestep hard-hitting sanctions, Iran has been subjected since June to a series of UN, US and EU measures aimed at its important energy sector.

While Iran has insisted the sanctions are having no effect, political analysts say the unexpected severity of the measures may have been a factor in bringing it back to talks.

Whether the visit would be useful for IAEA ambassadors would depend on what facilities they were allowed to see and whether they were permitted to bring technical specialists on their delegation, Sick said.

'My inclination on these things is not to just say 'No, we're not interested',' Sick said. 'It is the sort of thing that might be done for propaganda purposes, but might also be used for very useful purposes.'

He said the invitation could also be an initiative by Iran's new caretaker foreign minister, Ali Akbar Salehi, who took office last month. Salehi is a former Iranian representative to the IAEA, who would personally know the diplomats Tehran was inviting.

'This may be a gesture that was his idea, to bring in people and engage with them,' Sick said. 'He's a serious guy.' – Reuters