One of the key Iranian-backed warlords in Iraq threatening U.S. forces is a Shiite former member of parliament known as Abu Mahdi al-Muhandis.

Al-Muhandis is leader of the Kataeb Hezbollah, Arabic for Brigades of the Party of God, a Baghdad Shiite organization that specializes in funneling weapons and explosives from Iran to other Tehran-backed militants across Iraq, among them the dismantled Mahdi Army militia of firebrand cleric Moqtada Sadr.

Kataeb Hezbollah, branded a terrorist organization by the U.S. State Department, is an important part of the elaborate web of clandestine networks in Iraq that U.S. commanders say is run by Tehran to destabilize it as American forces withdraw.

Al-Muhandis, 56, is widely known as "the Engineer," one of the 19 aliases he's reputed to use.

The U.S. Treasury Department noted in July 2009 that al-Muhandis, a longtime clandestine operative for Iran's Islamic Revolutionary Guards Corps, was involved in the bombing of the U.S. and French embassies in Kuwait in December 1983 during the 8-year Iran-Iraq war.

Those attacks -- the United States and France were supporting Iraq -- were seen at the time as a joint operation by the underground Shiite ad-Dawa party and Hezbollah of Lebanon, two of Tehran's deadly surrogates in the region.

Al-Muhandis was also implicated in the attempted assassination of the emir of Kuwait, Sheik Jaber al-Ahmed al-Sabah, in a suicide bombing May 26, 1985, in his capital.

Al-Muhandis was convicted in absentia by a Kuwait court for the embassy attacks and the attempt to kill the emir, a close U.S. ally who died in January 2006 at age 77.

He joined ad-Dawa, one of Saddam Hussein's most ferocious Shiite enemies, in the early 1970s.

After the 1983 bombings, he fled Kuwait to Iran and fought Saddam's army with the Badr Brigade, a force made up of Iraqi Shiites captured by Iran. He returned to Iran in 2003 after Saddam was toppled.

The white-bearded al-Muhandis has more influence in Tehran than most of his contemporaries because, U.S. officials say, he's the right-hand man of Gen. Qassem Suleimani, commander of the Revolutionary Guard Corps' clandestine operations arm, the Quds Force.

Suleimani has masterminded Iranian covert operations in Iraq since before the U.S. invasion.

Unlike most of his contemporaries, al-Muhandis makes no secret of his links to Tehran.

"It's no secret that Iran's influence runs deep in Iraq," security analyst Thomas Strouse observed in a report on Iran's murky machinations in Iraq for the Jamestown Foundation, a Washington think tank.

"Most Iraqi politicians with close ties to Iran, however, are wary of tarnishing their nationalist credentials by admitting that they prefer to cooperate with Iran rather than the United States, in part because of growing anti-Iranian sentiment in Iraq."

Suleimani's Quds Force has armed, funded and trained Kataeb Hezbollah and other Shiite militant groups in Iraq to further Tehran's strategic objectives in bringing its historical enemy under is thumb since George W. Bush got rid of Saddam Hussein, the main Arab buffer against Iranian expansion.

While Kataeb Hezbollah, formed in early 2007, isn't the most powerful of the Shiite groups, it's considered one of the most important for its links to other anti-U.S. organizations.

It's not just in the gunrunning business. Between March 2007 and June 2008, the group, with an estimated strength of 2,000 operatives, repeatedly attacked U.S. forces using bombs, mortars, rockets, rocket-propelled grenades and snipers.

On July 2, 2009, the U.S. Treasury designated Kataeb Hezbollah and al-Muhandis as threats to the peace and stability of Iraq under Executive Order 13438.

The Quds Force was designated a terrorist organization by the Treasury Department Oct. 25, 2007.

The U.S. military says that Lebanese Hezbollah, which after years of guerrilla warfare drove Israeli forces out of south Lebanon in May 2000 to end 22 years of occupation, has helped to train and fund al-Muhandis' organization and those associated with it since 2006.

Hezbollah has repeatedly denied that. But Arab intelligence sources say that in recent months Hezbollah has stepped up activities in Iraq alongside the Quds Force as part of Tehran's push to dominate the country.

Al-Muhandis reportedly accompanied Revolutionary Guard commander Gen. Ali Jafari when he visited Damascus Aug. 21 to coordinate with Hezbollah, which is supported by Syria.