Iran fired another round of missiles in the Gulf early yesterday, clearly riled that the West had reacted dismissively to its earlier volley of long-range and short-range missiles and angered that its latest warnings on Iranian military retaliation have provoked little more than contemptuous indifference.

The United States reiterated its support for Israel and other allies in the region. But US officials made it clear that they did not see the missile tests as an immediate military challenge, nor did they believe that the escalation in tension would lead to war between America and Iran. Their reaction is astute. It gives Iran no excuse to portray itself as the victim of Western aggression. It undercuts the attempt by President Ahmadinejad and zealots in the Revolutionary Guards to provoke a fresh confrontation as a way of diverting domestic attention from their own failures. And it allows the West to focus on steadily increasing economic pressure to isolate the hardliners in Tehran and widen the split with pragmatists angered by their antics.

Mr Ahmadinejad has been doing his best to provoke. He has called for US military bases across the world to be “eradicated”. He has insisted that the sea, surface and air missiles were able to hit Israel while promising to strike at Tel Aviv, as well as US interests and shipping, if Iran were attacked. And he has warned the world that Iran, if provoked, would close the Strait of Hormuz, gateway for 40 per cent of global oil supplies.

His motives are transparent. Mr Ahmadinejad is isolated and deeply unpopular. Iran's economy is a shambles. Inflation is running at about 14 per cent. Almost one in three Iranians is unemployed, with young people, the bulk of the population, especially hard hit. The stench of corruption is everywhere. Far from fulfilling his campaign promise to put Iran's oil wealth on the plates of the poor, Mr Ahmadinejad's adventurism has kept oil production running far below its potential, as ageing infrastructure is denied key Western technology. Most humiliating of all is the need to introduce petrol rationing, since Iran cannot refine enough fuel for domestic use.

Manufacturing a foreign crisis is the resort of all unpopular rulers. Mr Ahmadinejad joins the Argentine junta, the Greek colonels and Slobodan Milosevic in the squalid attempt to whip up nationalist support to outflank domestic opposition. For there is little doubt that his domestic rivals are hoping he will stumble: as one hard-liner revealed, after being sacked from the Cabinet last month, the President can tolerate no dissent and therefore fills all appointments with political cronies rather than competent experts.

The West's refusal to respond to his belligerent rhetoric must be especially galling. It is doubly effective, however, when coupled with economic pressure. Last month Britain announced that it was freezing the assets of Iran's biggest bank. Yesterday Total, the French energy multinational, said it was pulling out of a huge gas project in Iran's South Pars field because the deal was too politically risky. It is a body blow to Iran's ambitions over liquefied natural gas. Total was the last big Western company still considering investment in Iran, and one of the few with the technology to exploit its huge gas reserves. Its move will significantly strengthen the sanctions imposed by the UN in response to Iran's nuclear defiance.

There should be no complacency about the latest Iranian threats. Rhetoric always runs the risk of becoming reality, and Israel is especially sensitive to such ranting. The West's best response is a clear warning, coupled with an insistence on continuing talks on Iran's nuclear programme. Mr Ahmadinejad is fast running out of excuses for prevarication.