As war clouds loom over Iraq and a nuclear disclosure makes North Korea suddenly relevant again, the third member of the "axis of evil" is fast approaching a decisive moment in its relationship with the west. Iran appears at last to be leaning in the right direction: the news at the weekend that Iranian security forces detained at least one of Osama bin Laden's sons along with several hundred people suspected of having links to the al-Qaeda organisation is the most recent indication of the change of mood. Moreover, Iranian officials are now signalling grudging support for the US campaign against Iraq and an even more reluctant, but real, willingness to lessen tensions with Israel. The Bush administration must acknowledge these desires for better relations with the west - or risk derailing the war on terrorism.
Iran qualified for the exclusive "axis of evil" triad thanks to its serial support for terrorism and determined pursuit of nuclear weapons. And the reality is that both of those charges still largely apply. But Iran's competitive internal politics always differed from the stark dictatorships of Iraq and North Korea and political debate has slowly produced a rough consensus in Tehran around the need to use the present circumstances to rationalise Iran's relations with Washington.
This conclusion emanates from a recognition among all of Iran's fractious factions that the country has suffered from its insistence on remaining on the sidelines in each of the region's post-cold war conflicts. Iran proved a constructive bystander during US military actions against Saddam Hussein in 1991 and against the Taliban regime in Afghanistan more recently. Still, official intransigence in dealing with the US meant that, in both cases, Tehran's co-operation went unrewarded. This time, with public opinion in favour of reaching out to Washington, Iranian political groups of all complexion are loath to let the opportunity pass.
Iran is an unlikely ally in the impending US campaign and it is also an uneasy one. Concerns about the dangers posed by Iraq are matched by anxieties about the projection of US power on Iran's periphery. This mixture of opportunity and threat initially sparked unease in Iran - if not active opposition - to US war plans. However, in recent weeks Iran's usually cantankerous clerics have signalled a readiness to be helpful. The bitter memories of the Iran-Iraq war, in which 20,000 of its soldiers were killed by Iraqi chemical weapons, are seared on the country's collective conscience - even today, Iran continues to see Mr Hussein's regime as an existential threat.
The intriguing aspect of this shift in Iran's perspective is that it is driven by the conservatives, who control the levers of power. Former president Ayatollah Hashemi Rafsanjani, Iran's foremost power broker, has even appropriated George W. Bush's rhetoric, calling Iraq's manufacturing programmes for weapons of mass destruction evidence that "it is an evil state".
Beyond rhetoric, Iran has taken certain steps to buttress its new policy. Tehran has allowed the Supreme Council for Islamic Revolution, the Iran-based Shia opposition group, to co-operate with the US, while intimating to visiting Kurdish delegations that it is prepared to assist the cause of overthrowing Mr Hussein.
These pronouncements from the conservatives are not limited to the issue of Iraq; they are now speaking openly about the need for improved relations with Washington across the board. Other prominent conservatives hint unashamedly about their openness to negotiations with the US, while a close ally of Ayatollah Ali Khamenei, Iran's supreme leader, has opened an office in Dubai for this purpose.
This new pragmatism may also be affecting Iran's long-held belligerence toward Israel. In a little-noticed statement recently, Iran's Foreign Ministry offered an unprecedented endorsement of a two-state solution to the Israeli-Palestinian conflict. This position drew fire from Hamas, one of its radical Palestinian clients, which blasted Tehran for "taking steps which are not acceptable in Islamic terms".
The Bush administration's resolute war against terrorism and its expressed determination to put pressure on recalcitrant regimes has yielded fruit in an unlikely place. As Tehran modifies its belligerence, Washington should ease some of its own prohibitions.
US-Iran relations are hardly on the verge of normalisation, as Tehran continues to seek weapons of mass destruction and has yet fully to extricate itself from the Arab-Israeli conflict. But a more nuanced policy is evident. Washington should engage Iran over Iraq and assure Tehran that its interests will be taken into consideration as the US plots its strategy.
At the same time, the US should remain vigilant and disrupt Iran's nuclear research programme, while putting pressure on Tehran to follow up on its recent declarations on Israel.
Through such a gradual and subtle approach, the US can not only secure an important ally for its campaign against Mr Hussein but also slowly compel Iran's leadership to transcend the ideological traps that have alienated its own population.
The writer is a fellow in international security studies at Yale University