The announcement that the United States would withdraw its troops from Iraq by 2011 caused much furor in Washington but it must have caused the ayatollahs in Iran even more excitement.

Clearly the regime's unelected Supreme Leader Ali Khamenei was left to ponder how best to coordinate the terrorist activities of the Revolutionary Guards Qods Forces in Iraq in this time frame.

Tehran is the main sponsor of the terrorist militias that are now claiming the lives of Coalition troops and ordinary Iraqis. There have been frequent finds of large caches of Iranian-made weapons in some of Iraq's most turbulent regions; and earlier this year Gen. Raymond Odierno, the new top commander of U.S.-led forces in Iraq, blamed the Iranian regime for 80 percent of all roadside bomb attacks on his troops.

In May 2007, President Bush warned that once a deadline for withdrawal was set, "all the terrorists would have to do is mark their calendars and gather their strength - and begin plotting how to overthrow the government and take control of the country of Iraq."

Such a ghastly scenario could end up posing the biggest foreign policy challenge to President Barack Obama when he takes over at the White House in January; and the solution surely is to tackle the threat now before the regime is able to further expand its tentacles of terror and dominion across all of Iraq.

On Aug. 20, President Bush made the point that the war on terror could not be won if terrorism was treated primarily as a matter of law enforcement. "We must," he said, "use all assets of national power to keep the pressure on the enemy, keep the extremists on the run, and keep the American people safe from harm."

One asset of national power that can and should be used is principled policy to tackle long-term strategic threats rather than the appeasement of terrorist-sponsoring states.

Iran has an overwhelmingly young population longing for change. And it has an organized Resistance movement capable of bringing democracy without the need for foreign military intervention.

Iran's main opposition group, the People's Mujahideen (PMOI), situated in Camp Ashraf in the Iraqi province of Diyala, poses the greatest strategic threat to the mullahs' rule. It has been instrumental in inspiring campus protests by Iranian students. Its supporters inside Iran have helped it to expose the regime's secret nuclear sites. In Iraq, it recently received the backing of some 3 million Shi'ites, who signed a petition welcoming the group's presence in the country and calling for the regime's expulsion from Iraq. Furthermore, in the Iraqi Parliament the Sunni bloc has come out squarely in support of the presence of the group in Iraq as the greatest barrier to Iranian influence there.

Meanwhile, Tehran has been plotting to force the Iraqi government to expel the group; but all its members in Iraq enjoy "protected persons" status under the Fourth Geneva Convention, meaning they cannot be expelled from the Country or involuntarily displaced.

Unfortunately, this did not prevent the Iraqi government under pressure from Tehran issuing a directive on June 17 calling for the group's expulsion and for the prosecution of its senior officials. And it recently asked U.S. forces to end their protection of Camp Ashraf.

It is very worrying that the United States should contemplate handing over the security of Ashraf to the Iraqis. Doing so would be to violate the Convention which provides that "protected persons" must not be handed over to an authority that seeks to breach their rights under the Geneva Convention. And it could well lead to the massacre of the 4,000 Iranian opposition figures residing in Ashraf.

Such action against the PMOI would also of course have far-reaching repercussions among Iraq's Sunni population, who would view what happened as a sign of Shi'ite Iran's domination of Iraqi affairs and a breach of the U.S. promise to resist Iranian intrusion. And with U.S. troops set to withdraw in 2011, the Sunnis and other nationalist Iraqis may end up relying less on the United States and find it more reassuring to bear arms themselves against anyone remotely associated with the Islamic Republic.

Gen. Odierno, who gained top marks in Baghdad and Washington last year for his strategy of a troop surge to combat Iranian meddling in Iraq, would do well to make sure his forces continue to protect Ashraf, not just to prevent a human tragedy but to avoid the disintegration of Iraq's hard-earned but fragile state of security.

Lord David Waddington is a former British home secretary under Prime Minister Margaret Thatcher and former leader of the House of Lords.