One of the White House's primary goals in its efforts to enhance US national security must be a security-based agreement with Iran. The US government is justified in strongly objecting to Iran's skewed parliamentary elections last month and the anti-democratic policies of Tehran's theocracy. But, like it or not, there are now powerful and pragmatic conservatives in the Iranian regime who could deliver results. And US security would be immeasurably enhanced if Iran abandoned its nuclear weapons aspirations and its support for terrorist groups in exchange for security guarantees from Washington and an easing of economic sanctions.

After 25 years of mutual suspicion, the path to such an accommodation will be lengthy and demand distasteful concessions on both sides. But now is the time to lay out a road map specifying the actions each side must take.

First, Iran must abandon all nuclear weapons ambitions by forswearing the goal of obtaining or acquiring the capability to produce nuclear weapons, including an indigenous nuclear fuel cycle that could be used to enrich uranium. Observers believe Iran has been pursuing nuclear weapons for years and today its leaders insist on the right to develop nuclear power with technology that could also produce a bomb. Tehran struck an agreement with the European Union last year to suspend enrichment of uranium, make a complete declaration of its nuclear program and agree to intrusive International Atomic Energy Agency inspections. If implemented, these steps might produce positive results in terms of Iran's move away from seeking nuclear weapons. But reason for skepticism remains.

The inspections led to disturbing findings. An IAEA resolution approved last week criticized Iran for an incomplete declaration, including omission of attempts to develop an advanced centrifuge and failure to explain traces of highly radioactive material at its facilities. US officials welcomed the resolution as proof of growing international impatience with Iran. Washington must now close ranks with the Europeans and other allies on this. Should there be no progress by June's IAEA meeting, the matter should be referred to the United Nations Security Council - with the prospect of sanctions against Iran and a mandate for more intrusive inspections.

Under any agreement with the US, Tehran must also surrender all known members of al-Qaeda; Iranian leaders readily acknowledge they are holding such people, in large part as a bargaining chip for negotiations with the US.

Last, Iran must cease military support for Islamic terrorist groups such as Hizbollah in Lebanon and Hamas in the occupied territories. Iranian leaders claim readiness to resolve both issues in the context of a larger deal.

The US, for its part, should offer to guarantee Iran's security by renouncing at the top level any intention to force regime change. Tehran, to an extent not understood in Washington, urgently seeks guarantees and international respect.

Washington should acknowledge that the Islamic republic is a regional power with legitimate security interests and that it deserves a voice in regional security matters. The US should increasingly engage Iran in discussions about a future security structure for the Gulf.

If there is a thaw in security relations, the US should begin easing economic sanctions - initially by using "carve-outs" in sanctions for specific activities. Mutually beneficial US investment in Iran's energy sector is the eventual goal.

This road map will require time - probably up to two years - and success is far from assured. Mutual suspicion is so deep that a one-off "grand bargain" will not be possible; reducing tension must start through low-key confidence-building measures.

Iranian leaders correctly suggest that co-operation in Iraq is one opportunity; this would greatly facilitate US policy given the imminent June 30 transition to an interim Iraqi government. Iranians have good relations with and access to the Iraqi Shia majority and Grand Ayatollah Ali Sistani, the influential Shia cleric. According to recent testimony by George Tenet, director of the CIA, Iran wants "an Iraqi government that does not threaten Tehran, is not a US puppet, can maintain the country's territorial integrity and has a strong Shiite representation." Tehran's goals in Iraq are compatible with Washington's and the Bush administration should consider inviting the Iranians to testify at the war crimes trial of Saddam Hussein. Beyond Iraq, advance notification of each side's military maneuvers would also build confidence.

The case for a security deal will be attacked in some circles as a sell-out of Iran's democracy movement. Some warn that an Iranian breakthrough with the US would help legitimize a clerical regime that commands the support of only 15 per cent of the population. Such critics suggest that the US cast its lot with the student movement and other reformers.

This argument is flawed. The reform movement has failed to develop deep roots in Iranian society. With strong leadership from student organizations, it may re-emerge after perhaps five years of reorganization and building bridges to civil society. Iran's future political system will anyway be determined by Iranians. America's primary interest is in stopping Iran's nuclear weapons development and support for terrorism. Washington should continue to express support for democracy, but not at the expense of efforts to overturn policies that threaten US security.

Given the threat that Iranian policies pose to US national security, the US must give this security accommodation a shot. Patience and a readiness to accept setbacks will be necessary. But if Washington succeeds, US security will be fundamentally enhanced.

Cliff Kupchan is Vice President and Senior Fellow at The Nixon Center in Washington, and a former US State Department official; he visited Tehran last month and met Iranian officials.

This article is reprinted as it appeared in the Financial Times.