Iran's Nuclear Activity

Iran has been conducting a sort of grand military parade up and down the Gulf this week, displaying its defensive hardware, test-firing sophisticated-sounding new weapons systems, and proclaiming its readiness to repel all would-be aggressors. Revolutionary Guard General Yahya Rahim Safavi, commander of the "Great Prophet" exercises, declared that Iran was now able to "confront any extra-regional invasion".

Neighbouring Sunni Arab states locked in political and territorial disputes with Tehran's Shia leadership may feel duly intimidated - not that any of them were planning to attack. A new high-speed torpedo called Hoot (meaning whale), so-called "flying boats", and various "radar-avoiding" surface-to-sea missile launches may also have seriously frightened local marine wildlife.

But the US, the principal intended audience of Iran's martial ostentation, is unimpressed. "We know the Iranians are always trying to improve their weapons systems," a Pentagon spokesman said yesterday. "The Iranians have also been known to boast and exaggerate their technical and tactical capabilities."

The US has repeatedly declined to rule out military action if coercive diplomacy fails to resolve the dispute over Iran's nuclear activities. And if the issue at hand is relative US-Iranian military might, it is really no contest. Total US defence-related spending will rise this year to around $550bn (£315bn); Iran allocated $4.4bn to defence in 2005. It cannot begin to match US weapons, technology and expertise.

Iran's great strength is its manpower: an army numbering 350,000 soldiers, plus 125,000 Revolutionary Guards, says the International Institute for Strategic Studies. Yet such an imposing host will be of little use if any future attack on Iran's suspect nuclear facilities is directed, as is thought likely, from the air.

Because of western sanctions, ostracism and a lack of spare parts, Iran has few modern fighter aircraft, although Russia recently proposed a $1bn sale of 29 Tor-M1 missile systems for anti-aircraft defence. The air force still relies in part on Iraqi MiGs flown to Iran for safety by Saddam Hussein at the start of the Gulf war in 1991 and never returned. Michael Knights, writing in Jane's Intelligence Review, said Iran was likely to try to repel any attack though a mobile defence of "highly integrated local networks of interceptor aircraft and ground-based Sams [surface-to-air missiles]". This would provide "layered protection" for strategic locations such as the Isfahan and Bushehr facilities and Bandar Abbas at the mouth of the Gulf.

While Great Prophet may have failed to predict Iranian military success, it has made a number of discomfiting points to the US and its allies. By focusing on the Strait of Hormuz, Iran reminded the west that up to one third of the entire world's exported oil supply must pass through a channel that American strategists call a "global chokepoint". The exercises alone have driven up crude oil prices.

American planners, trying to anticipate Iran's likely response to an attack, say it could block the strait using mines. Un-named intelligence officials told the Washington Post this week that there was a "growing consensus" that, if attacked, Iran would also resort to terrorism against civilian targets in the US and Europe, and would use Hizbullah and Islamic Jihad to foment trouble in Israel-Palestine, Lebanon and Iraq. No evidence was cited for these claims.

By highlighting external threats, this week's exercises have propaganda value for President Mahmoud Ahmadinejad's government, anxious to shore up domestic support for its hardline stance. Iran's rejection of the UN's 30-day deadline for nuclear compliance was reaffirmed yesterday by the foreign minister, Manouchehr Mottaki.

Parading its own capabilities, the US has meanwhile made a point of publicising tests in Nevada of "deep penetration" bunker-buster bombs that could be used against underground nuclear facilities. And moving perilously close to "enemy lines", it plans its own naval exercises in the Gulf next month. The codename? Arabian Gauntlet.