America’s allies and increasingly the American public are playing a ghoulish guessing game: Will President Bush manage to leave office without starting a war with Iran? Mr. Bush is eagerly feeding those anxieties. This month he raised the threat of “World War III” if Iran even figures out how to make a nuclear weapon.

With a different White House, we might dismiss this as posturing — or bank on sanity to carry the day, or the warnings of exhausted generals or a defense secretary more rational than his predecessor. Not this crowd.

Four years after his pointless invasion of Iraq, President Bush still confuses bullying with grand strategy. He refuses to do the hard work of diplomacy — or even acknowledge the disastrous costs of his actions. The Republican presidential candidates have apparently decided that the real commander in chief test is to see who can out-trash talk the White House on Iran.

The world should not allow Iran to have a nuclear weapon, but there is no easy fix here, no daring surgical strike. Consider Natanz, the underground site where Iran is defying the Security Council by spinning a few thousand centrifuges to produce nuclear fuel. American bombers could take it out, but what about the even more sophisticated centrifuges the administration accuses Iran of hiding? Beyond the disastrous diplomatic and economic costs, a bombing campaign is unlikely to set back Iran’s efforts for more than a few years.

The neocons pushing an attack on Iran admit that a prolonged bombing campaign would be necessary and would likely only delay Iran’s program. But it is still worth it, they say, and if everybody gets lucky maybe the attacks will unleash that popular uprising against the mullahs they’ve been promising for years.

That is the same kind of rose-petal thinking that was used to sell Americans a fantasy about the invasion of Iraq. Large numbers of Iranians are fed up with their government’s corruption and repression and with being branded a pariah state. Rain down American bombs, however, and the mullahs and Iran’s Holocaust-denying president, Mahmoud Ahmadinejad, are more likely to be turned into national heroes than hung from lampposts. And that’s not even calculating the international fury or the additional mayhem Tehran could wreak in Iraq or what would happen to world oil prices.

Secretary of State Condoleezza Rice is the other great hope (after Defense Secretary Robert Gates) for holding off a war. She still wants to give sanctions and diplomacy a chance. But, as with everything else she does, there’s nowhere near enough follow-through. If the stakes are really that high — and they are — then Ms. Rice and her boss must tell Moscow, Beijing and the Europeans that relations will be judged on whether they are willing to place a lot more pressure on Iran.

They also need to offer Iran a credible way back in from the cold — and clear rewards and security guarantees if it is willing to give up its nuclear ambitions. If it’s really that important — and we believe it is — then it’s time to send somebody higher ranking than the American ambassador in Baghdad to deliver the message.

For this to have any chance, Mr. Bush will have to tone down the rhetoric. Sure, a lot of these countries are letting greed cloud their judgment, when they balk at restricting trade with Iran. But it’s a lot easier to justify when they say they’re not giving the crazy American government an excuse for another war.

Maybe the country will get lucky and Mr. Bush will listen to the exhausted generals. But this isn’t just about surviving the rest of his presidency. Fifteen more months of diplomatic drift will bring Iran 15 months closer to figuring out how to make a nuclear weapon.