The strength of response of European governments to the crisis in Tehran is a welcome — if surprising — step. It has been made possible by President Obama’s considered restraint, reversing the pattern of the past two decades when the US has talked tough to Iran while Germany and Italy, more than others, have protected their commercial ties with Iran.

The EU governments’ new tough talk will not change the outcome within Iran. That will depend on how much the followers of Mir Hossein Mousavi are prepared to risk, whether they can carry many in the military with them (so far not) and how much violence the regime is prepared to use in putting down the uproar. A lot, we should assume. The bloodiness of the 1979 revolution is one indication; so, explicitly, are the warnings by Supreme Leader Grand Ayatollah Ali Khamanei that he would hold Mousavi and others responsible for deaths and injuries by the security forces.

But in making its calculations the regime cannot ignore the international opprobrium and penalties that would follow a brutal crackdown — that is, one even worse than there has been already. Yesterday Italy said that it was willing to open its embassy in Tehran to wounded protesters in co-ordination with other European nations. Italy and Germany are Iran’s biggest EU trading partners. Italy’s move follows Sweden’s question to other European Union countries of whether they might jointly open their embassies to demonstrators, a discussion that has not yet gone far but sends a signal to Tehran about the strength of feeling across the EU.

Britain, inevitably, has come in for specially sharp attacks from Tehran after Gordon Brown’s condemnation of the handling of the election, on top of the deep-seated Iranian suspicion of British designs on the country. Britain and France, with the US, have argued for tougher sanctions against Iran for continuing with its nuclear programme.

Compared with the Iranian security forces’ tactics in putting down the protests, these gestures from the European wings might seem irrelevant. But Iran can’t afford to ignore international reaction in the way that it could if its economy were stronger and if it was closer to achieving its goal of being the region’s undisputed power. Yesterday oil dropped below $68 a barrel. The falling price, and the turmoil, will deter foreign oil companies from making the investment that Iran desperately needs, given 30 years of underinvestment. If the US does pursue tougher sanctions over Iran’s nuclear programme then it will stand much more chance of success with committed EU support.

True, Iran is picking up a few small allies, as well as having Russia, China and India on its side. Yesterday the United Arab Emirates appeared to side with Tehran over its complaint of foreign meddling. No doubt this is unconnected with the three-day air force exercises that Iran (owner of the largest navy in the Gulf) began conducting there yesterday. But most Arab countries — Saudi Arabia above all — have been gloating at the setback suffered by Iran’s aims of becoming the region’s great power.

The US and other governments rightly have been cautious about giving verbal encouragement to Mousavi supporters when they can give nothing beyond that. Inevitably, they must wait and see how the uproar develops. But the EU, which has been half-hearted over Iran’s nuclear programme, has now taken a usefully outspoken role. It is one that Iran cannot ignore even if, ultimately, it is what Obama says that counts.

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