by Marc Burleigh

TEHRAN - 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.

Premature attack

The top US military commander said he believed it would be "premature" to take military action against Iran in response to its nuclear program in an interview to be aired Sunday.

General Martin Dempsey, chairman of the Joint Chiefs of Staff, also told CNN's "Fareed Zakaria GPS" program that economic sanctions have to be given a chance to work, and the United States and its allies should be better prepared for a military option.

"I think it would be premature to exclusively decide that the time for a military option was upon us," Dempsey said, according to excerpts of the interview released by CNN.

"I think that the economic sanctions and the international cooperation that we've been able to gather around sanctions is beginning to have an effect," he added.

In recent weeks, there has been feverish speculation that Israel was getting closer to mounting a preemptive strike on Iran's nuclear facilities, but Israel has denied reaching such a decision.

Tensions between Iran and Israel have also been simmering with Iranian warships entering the Mediterranean through the Suez Canal in a show of "might", a move Israel said it would closely monitor.

The United States, other Western powers and Israel believe that Iran is seeking to build a nuclear bomb, but Tehran denies the charge, insisting its atomic program is for purely peaceful purposes.

Iran said last week it was ready to resume stalled talks on its nuclear drive, prompting a cautious welcome from the United States and the European Union.

Dempsey said he believed that "diplomacy is having an effect" and suggested that even if the West opted for a military solution, it had to be better prepared for such a step.

"I mean, fundamentally, we have to be prepared," he said. "And that includes, for the most part, at this point, being prepared defensively."

Asked if Iranian leader were acting rationally, the US military commander said: "We are of the opinion that the Iranian regime is a rational actor. And it's for that reason, I think, that we think the current path we're on is the most prudent path at this point."

No oil

 Iran has halted its limited oil sales to France and Britain in retaliation for a phased EU ban on Iranian oil that is yet to take full effect, the oil ministry said on Sunday.

"Oil sales to British and French companies have ceased," spokesman Ali Reza Nikzad Rahbar said in a statement on the ministry's official website.

"We have taken steps to deliver our oil to other countries in the place of British and French companies," he said.

The decision was not expected to have a big impact. France last year bought only three percent of its oil -- 58,000 barrels a day -- from the Islamic republic, and Britain was believed to be no longer importing Iranian oil.

But it was seen as a warning shot to other EU nations that are bigger consumers of Iranian oil, including Italy, Spain and Greece.

Although those countries were not affected by Iran's announcement on Sunday, they are included in an EU decision to stop buying Iranian oil that was announced last month and which will take full effect from July.

The EU move was part of a ratcheting up of Western economic sanctions on Iran over its disputed nuclear programme. Many Western nations fear the programme masks a drive to develop nuclear weapons, but Tehran denies that.

According to the International Energy Agency, Italy sourced 13 percent of its oil, or 185,000 barrels per day, from Iran, while Spain imported 12 percent of its oil needs, or 161,000 bpd, and Greece bought 30 percent of its needs, or 103,000 bpd.

Iran, OPEC's second-biggest exporter after Saudi Arabia, pumps 3.5 million bpd of which it exports 2.5 million barrels.

Seventy percent of the exports go to Asian countries, China and India especially. More than 20 percent, or around 600,000 barrels per day, go to the European Union.

Iran has been threatening for weeks to cut all oil exports to Europe because of the EU ban, but has thus far held off. Ceasing all exports to the EU would harm its own economy unless it had Asian buyers ready to pick up the contracts.

Last Wednesday, the foreign ministry "invited" the ambassadors of France, Greece, Italy, the Netherlands, Portugal and Spain to individual meetings to explain to them that Iran "will revise" its oil sales to their countries.

Oil prices spiked on the warning, driven higher by an incorrect report on an Iranian television network, Press TV, that the halt in exports to the EU had already been implemented.

Iran's government then said it would not stop exports "at the moment."

But a foreign ministry official, Hassan Tajik, was quoted as saying: "Our message is that we can immediately replace our oil customers."

The European Commission said that even if Iran did cut its sales to the European Union, it would make little difference as EU buyers were already switching suppliers, particularly towards Saudi Arabia.

Iran has reacted furiously to a promise by Saudi Arabia -- a US ally and longtime rival in the Middle East -- that it will step in to pump more oil to compensate for any loss to the market from curbed Iranian exports.

Such a move would be viewed as "unfriendly," Tehran warned. AFP