Iran is no longer actively supplying Iraqi militias with a particularly lethal kind of roadside bomb, a decision that suggests a strategic shift by Iranian leadership, US and Iraqi authorities said Thursday. Use of the armor-piercing explosives, known as explosively formed penetrators, or EFPs, has dwindled sharply in recent months, said Army Lt. Gen. Thomas Metz, head of the Pentagon office created to counter roadside bombs in Iran and Afghanistan. Metz estimated that US forces find between 12 and 20 of the devices in Iraq each month, down from 60 to 80 earlier this year. "Someone ... has made the decision to bring them down," Metz told reporters. Asked if the elite Iranian Republican Guard Corps has made a deliberate choice to limit use of EFPs, Metz nodded: "I think you could draw that inference from the data." Iraqi government spokesman Ali al-Dabbagh agreed Iran has curtailed its activity inside Iraq. He said he thinks Iran has concluded that a new security agreement between the US and Iraq poses no threat to Iran. Iran opposed the agreement as a blessing for foreign forces to remain in Iraq, and encouraged Iraq's democratic government to reject it. The United States has long claimed that Iran or Iranian-backed groups are using Iraqi Shiite militias as proxies to kill US troops in Iraq. Iran denies the Bush administration allegations that it supplies money and weapons, but independent analysts have said US evidence is strong, if circumstantial. The US cites the spread of powerful EFP roadside bombs as the clearest Iranian fingerprint. US military officers say they know the EFPs come from Iran because they bear Iranian markings and because captured militants have told them so. The workmanship is so precise they could only come from a modern factory with machine tools available in Iran but not Iraq. EFPs account for only about 5 percent of the roadside bombs found in Iraq but 30 percent of the casualties, Metz said. The US has never specified who in Iran's government it believes is responsible. But military briefers point out that the Quds Force branch of Iran's Revolutionary Guards, which report to Iran's supreme leader, has a history of supporting Shiite militants outside Iran. The Army has said EFP attacks declined late last year in apparent response to an Iranian pledge to Iraq's Shiite-led government that it would hold back the flow of weapons. By early 2008, however, the US was again accusing Iran of supplying EFPs. "It is my opinion, it is the policy of the Iranian government, approved to highest level of that government, to facilitate the killing of Americans in Iraq," CIA Director Michael Hayden said in April. US military officials have said it had caches of weapons with date stamps showing they were produced in Iran this year. Besides EFPs, the military said it found Iranian mortars, rockets, small arms and other kinds of roadside bombs. Metz said the use of roadside bombs, which the military calls improvised explosive devices or IEDs, is declining as overall violence goes down in Iraq. Use of the often crude ambush bombs increased in Afghanistan during the seasonal height in fighting this year. Pentagon statistics showed that in October, US and allied forces discovered 411 such bombs, down from 1,321 a year earlier and 2,529 in October 2006, when violence was raging across Iraq. Roadside bombs killed two coalition soldiers in October, down from 20 the year before and 74 in October 2006, the statistics showed. In Afghanistan, October figures were slightly lower this year than last, with 264 bombs discovered compared with 274 in October 2007. But the 2007 figure had represented a high for that year. Use of the bombs peaked in Afghanistan this summer, with figures above 300.