Much of the money is heading in one direction, though: Iraq is becoming dependent on imports because industries here have been ravaged by the economic sanctions of the 1990s and the current sectarian violence. Reconstruction and security have lagged so far behind the expectations of ordinary Iraqis that cheap goods from Iran and neighboring countries often provide the only comforts in their lives.

“What is happening in Iraq at the moment is a lot of trade, but it’s almost all one-way trade,” Barham Salih, the Iraqi deputy prime minister for finance, said of the country’s economic ties with Iran and other neighbors. “If you take oil away, there’s a lot of imbalance in this.”

Iraqi leaders from the Shiite bloc currently in power say political and economic ties with Iran, which is governed by Shiite Persians, will inevitably strengthen. As driving factors, they cite the hostility of Sunni Arab nations to a Shiite-run Iraq and the ambivalence of the White House toward the devout Shiite parties here.

“If the Shiites do not feel protected, if they feel what they’ve achieved can’t be maintained, much of the leadership will have to work with Iran,” said Sami al-Askari, a Shiite legislator who advises Prime Minister Nuri Kamal al-Maliki, himself a religious Shiite with close ties to Iran. “The Arabs and the Americans are saying Iran is bad, but it’s the only recourse.”

According to one commonly cited statistic, trade between Iraq and Iran has grown by 30 percent a year since the 2003 invasion. But American officials here say no accurate numbers are available because Iran refuses to release complete figures.