Washington (CNN) -- The single largest threat to Iraq's security today comes from Iranian-backed militia groups and the thousands of fighters, cash and weapons under their control, according to Maj. Gen. Jeffrey Buchanan, the spokesman for U.S. forces in Iraq.
Speaking to reporters at the Pentagon Tuesday, Buchanan said these groups now outpace al Qaeda in Iraq (AQI), which once controlled much of the insurgency that terrorized the country.
The United States suspects these groups were behind a number of deaths of U.S. troops in June, using weapons brought in from Iran. Some Iranian-made weapons have been found with manufacture dates as recent as last year, Buchanan said. Overall he said there is "a significant increase in support" from Iran's secretive Quds force, the elite unit of Iran's Islamic Revolutionary Guard.
Buchanan said he believes Iraqi government officials understand Iran's influence could pose a long-term threat and they have told Iran "to knock it off," but he emphasized that was his opinion only.
As for AQI, Buchanan said it still controls anywhere between 800 to 1,000 fighters, but the long-time use of foreign fighters coming into Iraq across the Syrian border has slowed to a trickle. Buchanan said AQI is now so desperate for funds it's engaging in robberies to get money, however the group is also beginning to establish "legitimate businesses" to finance its operations. He said, it will "take a long time to defeat them."
Buchanan also confirmed the United States is informally talking to Iraq about a continued U.S. troop presence in the country after the end of this year. He didn't rule out that troops could find themselves in combat in a new arrangement, but emphasized the expectation is Iraq will ask for help with training its troops.