EPA

PESSIMISTS think they have seen something like this before. Iran has a nuclear programme that outsiders say is designed to produce a bomb, but which the Iranians insist is not. America is making threatening noises. Some outsiders—such as a group of British think-tanks which released a report on the matter on Monday February 5th—worry that a military confrontation could provoke a yet nastier situation in which civilians are the main victims once again.

There are as many differences as similarities this time around, when compared with Iraq. Whereas Saddam Hussein's supposed chemical and biological weapons were among the stated reasons for America's invasion of Iraq, Iran raises the scarier prospect of getting a nuclear bomb within a few years. Such a weapon in the hands of a leadership that rejects Israel's right to exist concerns Westerners, just as an overly powerful Iran troubles many neighbours in the region. But nobody thinks America would invade Iran; far more likely, any strike would come only from the sky, and perhaps then conducted by America's ally, Israel. America's new secretary of defence, Robert Gates, was recently at pains to state that “we are not planning for a war with Iran.”

But some are worrying that increasing tension makes an unplanned war more likely. America has certainly piled on the pressure. The American government has made increasingly assertive remarks, notably about the influence of Iran inside Iraq. On Friday an American intelligence report cited “Iranian lethal support for select groups of Shia militants” there. Such remarks have been backed by the display of more military muscle in the region, including anti-missile batteries and a naval battle-group which are more suited for use against a conventional enemy than against Iraqi insurgents. In this tense atmosphere small incidents, such as the recent detention of Iranians by American soldiers in a diplomatic compound in northern Iraq, risk becoming an excuse for wider confrontation.

Iran is not shy of raising the temperature itself. On February 11th, the anniversary of 1979's Islamic Revolution, it is believed that Iran will claim to have made a big step forward in its enrichment of uranium at a centrifuge facility in Natanz. Iran has already enriched small amounts of uranium; it may say (though many will yet doubt it) that production on an industrial scale is soon possible. This may encourage Americans and Israelis who think some sort of military intervention is needed to act sooner rather than later.

Many in America are certainly worried about blundering into Iran. In recent days two Democrats running for president in 2008, Hillary Clinton and John Edwards, made it clear that they are opposed to strikes (though nearly all American leaders, of both parties, say no option should be permanently taken off the table). Mrs Clinton wants more dialogue; Mr Edwards wants to work with European and other allies to isolate Iran.

But neoconservatives and some traditional conservatives who have Mr Bush's ear say that Iran is irredeemably unreliable, and will use any diplomacy to play for time. They also warn that although Russia and China signed onto mild UN sanctions for Iran in December, diplomatic action will be blocked by the two powers (especially Russia) which remain loth to do much more.

An Iranian announcement of further nuclear progress could yet stiffen spines. Saudi Arabia said recently that it would try to keep oil prices stable at their current, lower levels. Besides worrying about the effects that the high prices have on the world economy, the Sunni kingdom may also be trying to put pressure on Iran, whose shaky economy depends on exports of hydrocarbons. Others see reason for optimism in recent criticism from within Iran of the president, Mahmoud Ahmadinejad. He was elected promising to improve the lot of the poor, but he may be losing support among both the masses, who have seen little gain in recent years, and in the clerical elite, who worry that he is too provocative of outside powers.

But there is no sign that Iran's regime is tottering. Nor is Mr Bush's administration wavering in its preference for confronting Iran. Any conflict could, at the least, further inflame troubles inside Iraq, Israel and the Palestinian territories, while driving up oil prices. It would also worsen relations between Muslims and the rest of the world. And though it may not be imminent, it is becoming easier to imagine.