Iran is to host a high-level team from the UN nuclear watchdog on Monday as part of efforts to defuse dire international tensions over its atomic activities through dialogue.

But other words being spoken in Israel, the United States and Britain -- and Iran's defiant moves to boost its nuclear activities -- underlined the prospect of possible Israeli military action against the Islamic republic.

Iranian Foreign Minister Ali Akbar Salehi on Sunday said his country was keen to quickly resume mooted talks with world powers, once a place and date were agreed.

The last talks collapsed in Istanbul in January 2011, but Iran has responded positively to an EU offer to look at reviving them.

"We are looking for a mechanism for a solution for the nuclear issue in a way that it is win-win for both sides," Salehi said.

But he added that Iran remained prepared for a "worst-case scenario".

Such a scenario -- war -- remained very much the subtext of a visit to Israel on Sunday by US National Security Advisor Tom Donilon.

Israel has been gripped by feverish speculation in recent weeks that it is closer to mounting a pre-emptive strike on Iran's nuclear programme, though Tel Aviv has denied reaching such a decision.

The United States, while itself not ruling out a military option against Iran, was publicly being seen holding back its main Middle East ally from taking such drastic action.

"I think it would be premature to exclusively decide that the time for a military option was upon us," the chairman of the US Joint Chiefs of Staff, General Martin Dempsey, told CNN.

"The US government is confident that the Israelis understand our concerns," The Jerusalem Post newspaper quoted Dempsey as saying in the CNN interview.

British Foreign Secretary William Hague also warned on the BBC on Sunday: "I don't think the wise thing at this moment is for Israel to launch a military attack on Iran.

Israel's calculations will have taken into account an announcement by Iranian President Mahmoud Ahmadinejad last Tuesday that his scientists were boosting uranium enrichment, notably by adding 3,000 more centrifuges to a facility at Natanz.

Iran also appeared to be about to install thousands of new centrifuges in another, heavily fortified enrichment facility near the city of Qom, a diplomat accredited to the UN nuclear watchdog told the BBC.

Iran says the enrichment is part of a purely peaceful civilian nuclear programme.

Western nations and Israel, though, fear it is part of a drive to develop the ability to make atomic weapons.

A November report by the UN nuclear watchdog, the International Atomic Energy Agency, strongly suggested Iran's programme included nuclear weapons research.

The IAEA delegation due in Tehran on Monday is to hold two days of talks with Iranian officials on those suspicions.

A previous visit on the same issue at the end of January, though, yielded no breakthrough.

"I'm not optimistic that Iran will provide much more information because I think any honest answers to the IAEA's questions would confirm that Iran had been involved in weapons-related development work and Iran wouldn't want to admit that for fear of being penalised," Mark Fitzpatrick of the London-based International Institute for Strategic Studies told AFP.

UN inspector hopes for 'concrete results' from Iran trip
Vienna (AFP) Feb 19, 2012 - The chief UN nuclear inspector on Sunday expressed hope that "concrete results" would emerge from his two-day visit to Iran, but cautioned that progress "may take a while."

"We hope to have a couple of good and constructive days in Tehran," International Atomic Energy Agency chief inspector Herman Nackaerts told reporters at Vienna airport before boarding a plane to Iran.

"Importantly we hope for some concrete results from this trip. The highest priority remains of course the possible military dimensions of Iran's nuclear programme, but we want to tackle all outstanding issues," he said.

"This is of course a very complex issue that may take a while. But we hope it can be constructive."

The visit led by Nackaerts is the second to Iran in three weeks and is seen as a key test of Iran's willingness to hold substantive talks with the IAEA about suspicious activities outlined by the agency in a November report.

Western diplomats to the IAEA said that the first trip, from January 29-31, was more of a confidence-building exercise, with the inspectors neither meeting key figures in Iran's nuclear programme, nor visiting any nuclear sites.

The IAEA's November report said Iran had carried out activities that were "relevant to producing" a nuclear weapon.

Since its publication, the United States and the European Union have ramped up sanctions on Iran's oil sector, and speculation has grown that Iran's arch rival Israel might launch military attacks on Iranian atomic facilities.

The Islamic republic, which denies seeking the bomb and which says the IAEA report was baseless, last week defiantly trumpeted advances -- downplayed by Washington as "hyped" -- in its nuclear programme.

Iran also signalled on Sunday that it is ready to hit back hard at sanctions threatening its economy, by announcing it has halted its limited oil sales to France and Britain.

Iran said last week it was ready to resume stalled talks on its nuclear drive with the P5+1 powers -- the US, Russia, China, France, Britain and Germany -- which broke down in Turkey in January 2011.