French expert: There will be no military strike on Iran

The first is Israeli air strikes designed to delay the nuclear programme.

The scenario would see Israeli F16s fly over Saudi Arabia to Iran in a one day operation that would likely achieve little in terms of damaging facilities.

The second is a bigger US-led campaign that would last several days, involve the use of strategic B-2 bombers flying from the US or Diego Garcia in the Indian Ocean, firing of naval-borne cruise missiles and parachuting in special forces to carry out sabotage, laser guiding and damage assessment.

The third option is a sustained US-led bombing campaign designed to cripple Iranian military infrastructure more broadly and to "shake the foundations of the regime." EU countries, such as France and the UK, would get involved only in the event of a mass-scale Iranian retaliation.

Tertrais believes none of this will happen, however.

"All these options are worse than sanctions. The only hope is that external pressure will force the regime to compromise, will make the cost of its nuclear efforts increasingly unbearable," he explained.

"The immediate consequences of military strikes would be a shock to the oil and gas markets and the world economy, as well as Iranian military retaliation - missile attacks on Israel, on Western allies in the [Arabian] Gulf, on military bases in Gulf countries and a new campaign of terrorism against the West."

He added: "The UN report is not going to be a trigger for military action. All the war talk from Israel should be seen in the light of domestic Israeli politics and trying to exert pressure on the international community to adopt an even harder line, to increase sanctions."

Existing UN sanctions comprise: an arms embargo; asset freezes and visa bans on people linked to the nuclear programme; and blocking of Iranian banks and shipping lines engaging in nuclear procurement activity.

The next step could be to blacklist the Iranian central bank, making it impossible for Iran to borrow money on international markets. But China and Russia have up till now threatened to veto extra steps at the UN Security Council.

The internal report by the Vienna-based nuclear watchdog, the IAEA, circulated to IAEA members on Tuesday night was immediately leaked to press.

The 12-page study signed off by IAEA chief, Japanese diplomat Yukiya Amano, states boldly that: "There are ... indications that some activities relevant to the development of a nuclear device continued after 2003, and that some may still be ongoing."

It also includes a 13-page annex giving never-before-published details of the alleged weapons programme. The annex cites "credible" information from Western intelligence agencies that Iran has bought black market know-how on making an enriched uranium weapons core and on fitting warheads to missiles, as well as carrying out tests on a sophisticated detonator.

Tertrais said it is "remarkable" that all 27 EU countries, including previous sceptics such as Austria, are "united" on the need for tougher sanctions.

But he predicted the UN report will not change China or Russia's point of view. "It should be a game-changer, but it won't. Those that don't want to be convinced won't be convinced," he said.