Tehran's Influence Grows As Iraqis See Advantages

"If we want to establish security in Iraq, the Iraqi government should take security into its own hands," he said. "Unfortunately, the others don't want that to happen."

Caught between the United States and Iran is Hoshyar Zebari, Iraq's foreign minister. "I'm treading a very thin line," he said last week over tea in his office. Zebari says he believes Iran wants a stable government in Iraq, along with the departure of U.S. troops, but is worried that a full-scale civil war could spill over Iraq's borders.

Iran supports the two largest Shiite political parties, the Supreme Council for the Islamic Revolution in Iraq (SCIRI) and the Dawa party of Prime Minister Nouri al-Maliki, U.S. officials have said. But Iran also negotiates with Kurdish and Sunni politicians and sometimes bypasses the central government to forge agreements with Iraqi provinces, Zebari said.

"Historically that has been their attitude, to bet on every horse. And they have changed their support from one group to another," Zebari said.

Some analysts say the violence and instability in Iraq attract more Iranian involvement, not less, as Iran positions itself to be on the winning side of a sectarian war.

"The whole Gulf system is turned upside down, and everybody is trying to figure out how they situate themselves in it," said Ray Takeyh, an Iran expert at the Council on Foreign Relations, referring to traditional relationships in the Persian Gulf region. Iranian support is "part of the program of strengthening the Shia community to resist and expand its influence, and become a successful combatant in a civil war."

For the Iraqi government, it has been a frustrating strategy. "Instead of diversifying your support or aid to different groups, militias, political leaders, if you're sincere in your commitment to see this government succeed, why don't you give all this assistance and money and weapons and training directly to the government?" Zebari said.

Iran has driven a wedge between Iraq and the United States. Last month, when U.S. troops seized two Iranian officials inside the Baghdad compound of Abdul Aziz al-Hakim, the leader of SCIRI, the Iraqi government intervened and the United States freed them. After U.S. troops seized five more Iranian officials from the liaison office in Irbil, the Iraqi government again appealed for their release -- so far unsuccessfully -- saying the men worked in an approved office providing consular services.

In both cases, U.S. officials accused some of the Iranians of being operatives with the al-Quds Brigade, which the Americans say arms and trains terrorist groups outside Iran, including the Lebanese organization Hezbollah and Islamic Jihad, which is active in the Palestinian territories. Both the Iraqis and Iranians have asked the United States for proof of clandestine activities.

U.S. officials decided to escalate their tactics against Iran after public denunciations of Iran's alleged military activities, along with attempts to "harden" Iraq's security forces to repel Iranian influence, failed to produce satisfactory results, Khalilzad said. "We've come to the view that we need to do more than that, we need to go after their networks," he said.

During the rule of Saddam Hussein, who oppressed Iraq's Shiites and fought an eight-year war against Iran, Iraqi Shiite dissidents in exile, especially SCIRI and its armed wing, the Badr Brigade, found welcome help from Iranian security forces.

"We know what the relationship between SCIRI, Badr and the Iranian institutions were in those days. Now it's a different situation," Khalilzad said. The Iraqi government is no longer "an opposition movement in need of support from the security agencies of a neighboring state, so there is a need for adaptation in terms of what's appropriate in terms of a relationship."

Iraqi officials are sharply divided in their perceptions of Iran's intentions in Iraq. Hussein al-Falluji, a Sunni member of parliament, said Iranian influence exceeds that of the United States, but it is "hidden, and is heading toward targeting vital joints of the Iraqi state."

Mowaffak al-Rubaie, Iraq's national security adviser, said, "Iran is networking aggressively inside Iraq in every aspect of life, including the security aspect."

Mariam Rayis, a foreign affairs adviser to Maliki, dismissed as paranoia U.S. assertions about Iran's "dark involvement" in Iraq. "These neighbors can help us for a while until we can have new construction here," she said. "We have noticed that there is moral support from Iran."

Special correspondents Naseer Nouri in Baghdad and Saad Sarhan in Najaf and other Washington Post staff in Iraq contributed to this report.