Gen. Ray Odierno said the attacks had decreased but were still a problem. He spoke just after the U.S. relinquished security for Baghdad and other urban areas to Iraqi forces, part of a security agreement that will see all American soldiers out of the country by the end of 2011.

"Iran is still supporting, funding and training surrogates who operate inside of Iraq," Odierno said at the U.S. military headquarters outside Baghdad. "They have not stopped, and I don't think they will stop. I think many of the attacks in Baghdad are from individuals that have been in fact funded or trained by the Iranians."

Tehran denies allegations that it is supporting violence in Iraq.

Odierno said the attacks were mainly indirect fire - a term usually reserved for mortars, rockets and artillery - and EFPs, or explosively formed penetrators. That last weapon is designed to attack armored vehicles such as Humvees and is among the main killers of U.S. troops in Iraq. U.S. officials have said the main component of the EFP is manufactured in Iran.

Odierno directly implicated groups supported by Iran in recent rocket attacks against the walled-off Green Zone in central Baghdad.

"Those are being done by groups that have been trained in Iran, been funded by Iran," he said. "Usually their leaders are still in Iran and they have surrogates doing operations in Iraq."

But, he said, the number of such attacks is "significantly smaller" as a result of security measures that make them more difficult to carry out.

Speaking later to Pentagon reporters by videoconference, Odierno said that work done by U.S. and Iraqi forces to go after Iranian surrogates, uncover weapons caches, and control the flow of weapons across the border had made it much harder for Iran to maintain the explosives supply.

He also said intelligence had not detected any changes since Tehran was gripped by massive street protests following charges of fraud in the June 12 presidential election. "They have kind of maintained themselves in a steady state as we've moved forward," he said.

On Monday, U.S. Ambassador Christopher Hill said he was concerned about military reports showing that illegal arms continued to flow into Iraq from Iran.

"I think the Iraqi government is taking a very tough-minded view of some of these insurgent groups that the Iranians have clearly been supporting over the last year or so," he added.

Hill also said that Iran was still trying to exert a "malevolent influence" over neighboring Iraq but that he was hopeful Iraqis aren't responding.