Earlier this month, US Vice- President Dick Cheney threatened Iran from the deck of an aircraft carrier. Two days later, the US announced direct talks with Iran on Iraq. The Bush administration wants to have it both ways, using threats as leverage to win diplomatic concessions in talks. But for negotiation with Tehran to succeed, threats won't work. That's because threats will only strengthen the hand of a powerful Iranian faction that is opposed to talks.

Washington needs to digest the realities of Iranian domestic politics. There are no pro-Americans in the Iranian government, but there are three factions of conservatives whose differing views matter.

First are the hardline conservatives headed by President Mahmoud Ahmadinejad, a faction that includes the head of the Revolutionary Guard, Yahya Rahim Safavi; the head of the Basij paramilitary, Mohammad Hejazi and the radical clergy. These powerful people want neither talks with the US nor anything to do with a rapprochement. Veterans of the war with Iraq, these men ardently distrust the US and could undermine talks or use them to thwart US interests. And so they are likely to use US military threats or the spectre of additional sanctions to claim that Washington is not serious about diplomacy and that its gestures of flexibility are aimed more at Europe than Iran.

The second and even more influential faction is the traditional conservatives, headed by Supreme Leader Ali Khamenei, who is a balancer among groups. This group has the final say on key issues, certainly including talks with the US It is leery but now supportive of talks; that stance could shift if Washington slings more threats at Tehran.

Finally, there are the pragmatic conservatives, headed by former president Hashemi Rafsanjani, Hassan Rohani and the recently arrested Hussain Mousavian. They support talks with the US, call for a less-aggressive nuclear and foreign policy and stress the importance of integration in the global economy and attracting foreign investments. This group is not part of the policy-making establishment, yet individuals such as Rafsanjani retain influence. Official talk from Washington about military action undermines this faction, the only one that is committed to giving diplomacy a chance.

Shaky foundation

In the best of circumstances, any diplomatic engagement will stand on a shaky foundation. Direct bilateral talks have a long history of near misses, most recently when Secretary of State Condoleezza Rice and Iranian Foreign Minister Manouchehr Mottaki attended the same conference on Iraq last month. The US and Iran have a 28-year history of vitriol; direct talks will be controversial in both countries.

Along with a cessation of threats, Washington should create an environment conducive to diplomacy. Rice's recent decision to attend an Iranian art exhibition in Washington was a step in the right direction. The National Basketball Association is about to crown a new champion; why not encourage NBA exchanges with basketball-crazy Iran. This month, a group of Iranian lawmakers began to form a US-Iranian friendship committee; legislative exchanges should be initiated.

Some will argue that one-track diplomacy, without threats, will signal US weakness. The argument is without merit. Tehran knows well that Bush has said that all options, including military, are on the table. And a period without chest-thumping in no way prevents a return to coercive diplomacy later if necessary.

Even threat-free talks may not work. On Iraq, the US will want Iran to stop arming Shiite militias and to encourage Shiite leaders Abdulaziz Hakim and Moqtada Al Sadr towards conciliation. Iran may not cooperate. The US will surely demand a suspension of uranium enrichment, but nobody in Tehran will agree to that.

Still, there's no time to waste. Iran's nuclear programme is progressing quickly, and that is underscored by Wednesday's announcement by the UN nuclear watchdog that Iran is actually accelerating its nuclear program. Iraq is taking a huge toll on the US. Israel's patience with Tehran's nuclear and diplomatic advances is growing thin. But US threats empower exactly those who challenge our vital interests. So while threat-free diplomacy is a long shot, it's our last, best chance, and we must try it.

Clifford Kupchan is a director at Eurasia Group, a political risk consulting company, and a former State Department official. Ray Takeyh is a senior fellow at the Council on Foreign Relations.