"We know that they are being in fact manufactured and smuggled into this country, and we know that training does go on in Iran for people to learn how to assemble them and how to employ them. We know that training has gone on as recently as this past month from detainees debriefs," Maj. Gen. William Caldwell, the U.S. military spokesman, said at a weekly briefing.
EFP stands for explosively formed penetrator, deadly roadside bombs that hurl a fist-size lump of molten copper capable of piercing armor.
In January, U.S. officials said at least 170 U.S. soldiers had been killed by EFPs.
Caldwell also said on Wednesday that the U.S. military had evidence that Iranian intelligence agents were active in Iraq in funding, training and arming Shiite militia fighters.
"We also know that training still is being conducted in Iran for insurgent elements from Iraq. We know that as recent as last week from debriefing personnel," he said.
"The do receive training on how to assemble and employ EFPs," Caldwell said, adding that fighters also were trained in how to carry out complex attacks that used explosives followed by assaults with rocket-propelled grenades and small arms.
"There has been training on specialized weapons that are used here in Iraq. And then we do know they receive also training on general tactics in terms of how to take and employ and work what we call a more complex kind of attack where we see multiple types of engagements being used from an explosion to small arms fire to being done in multiple places," Caldwell said.
The general would not say specifically which arm of the Iranian government was doing the training but called the trainers "surrogates" of Iran's intelligence agency.
Caldwell opened the briefing by showing photographs of what he said were Iranian-made mortar rounds, RPG rounds and rockets that were found in Iraq.