Two days after Mahmoud Ahmadinejad, the man who has sworn to annihilate Israel, declared that Iran’s nuclear program has “no reverse gear,” the Bush administration has apparently gone into reverse itself. Despite its declared policy of refusing to negotiate with Iran and Syria, the State Department has signalled that American officials will hold talks with representatives of both countries when Iraq holds two regional conferences this month and next.

In Europe, this policy shift is inevitably being seen as a humiliation for President Bush. “This is a major climbdown by the American government,” commented the Daily Telegraph, which nonetheless welcomed the move. Most European governments are terrified of the American military build-up in the Persian Gulf. Their worst-case scenario is an American or Israeli airstrike against Iranian nuclear facilities. Most Democrats and some Republicans in Congress — the “wise people of Washington,” as Mr. Ahmadinejad charmingly refers to them — apparently agree.

In reality, there are plenty of much worse outcomes than an airstrike against Iran, even leaving aside the one that the Iranian president says would be his best-case scenario: the end of the world, ushered in by the destruction of all infidels. Let’s consider one less dramatic but more likely scenario.

Iran negotiates with America, and the mullahs enjoy the spectacle of a hijab-wearing Condoleezza Rice shuttling between Washington and Tehran, while carrier battle groups are removed from the Gulf and Israel is bribed to keep shtoom. The modest U.N. sanctions regime is treated as a dead letter and the Iranians are able to step up their illegal imports of nuclear materials and technology.

In good time for the American presidential election, Iran carries out a nuclear test without warning, and an exultant Mr. Ahmadinejad announces that Iran now has both a nuclear capability and a delivery system capable of reaching Europe. Egypt, Saudi Arabia, Turkey, and Syria announce that they, too, are joining the nuclear club.

Iran has already bought a missile defense system from Russia designed to deter any American or Israeli attack. Later this year, Presidents Putin and Ahmadinejad meet in the Kremlin to conclude a mutual defense pact: any attack on either state would be regarded as an act of aggression by the other. The Putin-Ahmadinejad pact allows Iran to speed up its nuclear program and also establishes an energy cartel that controls much of Europe’s gas and oil supplies. Higher energy prices enable Russia to return to Soviet levels of military spending, inaugurating a new arms race with the West. The trans-Atlantic strains that this creates bring NATO near to collapse.

Meanwhile, the Iranians gain increasing influence over the Iraqi government. A British drawdown is followed by an American one, finally convincing the Iraqis that the West is not to be trusted. President Hillary Clinton and Vice President Obama are elected on a cut-and-run policy, but the precipitate withdrawal of coalition forces is followed by the creation of an Iranian puppet regime, civil war, and Iranian intervention. Apart from the original coalition of the willing, the United Nations acquiesces in the “Lebanonization” — in effect, the annexation — of Iraq by Iran.

With Islamism ascendant across the Middle East, Israel is faced by war on several fronts. Hezbollah and Hamas join forces with Iran, Syria, and the new Muslim Brotherhood-led government in Egypt. Americans watch helplessly as the threat of nuclear attack from Iran ties Israel’s hands. Most Europeans look the other way as Israel is subjected to a long-range war of attrition.

Al Qaeda, meanwhile, announces that it now has radioactive “dirty” bombs, chemical and biological weapons, which look suspiciously like those thought to have belonged to Saddam’s arsenal prior to his fall. A figure purporting to be Osama bin Laden issues an ultimatum: Unless NATO forces leave Afghanistan, major cities in Europe and America will be rendered uninhabitable.

Apart from the British, the Europeans pack their bags and flee. President Musharraf in Pakistan is toppled and replaced by a regime closely aligned with the Taliban. The original “Islamic bomb” is now in the hands of the Islamists.

The global jihad, it goes without saying, would continue unabated, while the West is forced to retreat step by step from the dominant position achieved by 2003. All this could happen without the Iranians even needing to use their nuclear weapons. Perhaps that is what Mr. Ahmadinejad means when he claims that Iran “poses no threat” to Israel or the West. Iran can cause havoc merely by having the bomb.

I make no apology for doom-mongering. The stakes could not be higher. If the Bush administration is serious about negotiating with Iran, Ms. Rice must go into these talks with one aim in mind: stopping the Iranian nuclear time bomb. Sitting down with the Iranians is already a concession. It should be the last one. Mr. Bush needs to use these meetings to send a signal to Tehran that they won’t forget. For in reality, I doubt whether Mr. Apocalyptejad would be as restrained as the above scenario presumes. If he once gets the bomb and the means to deliver it, everybody in Israel knows what will happen next. The rest is silence.