It appeared to be the first publicly disclosed instance of Iranian arms entering Afghanistan, although it was not immediately clear whether the weapons came directly from Iran or were shipped through a third party.
Gen. Peter Pace, chairman of the Joint Chiefs of Staff, said that unlike in Iraq, where U.S. officials say they are certain that arms are being supplied to insurgents by Iran's secretive Quds Force, the Iranian link in Afghanistan is murky.
"It is not as clear in Afghanistan which Iranian entity is responsible, but we have intercepted weapons in Afghanistan headed for the Taliban that were made in Iran," Pace said.
He said the weapons, including mortars and C-4 plastic explosives, were intercepted in Kandahar province in southern Afghanistan within the past month. He did not describe the quantity of intercepted materials or say whether it was the first time American forces had found Iranian-made arms in that country.
Asked about Pace's remarks, a Pentagon spokesman, Army Col. Gary Keck, said he had not heard of previous instances of Iranian weaponry being found in Afghanistan but he was not certain this was the first time.
Iran has had an uneven relationship with Afghanistan over the years. During the wars of the past quarter-century, millions of Afghans, particularly from the western provinces, took refuge in Iran.
In recent years Iran has contributed to numerous economic improvements in western Afghanistan, including roadways, schools and several clinics. But Michael Rubin, an Iran expert at the American Enterprise Institute, sees reason for concern about Iran's efforts to increase its influence inside Afghanistan.
"Iran's leadership often strikes pragmatic relationships to further their influence at our expense," he said Tuesday. "A lot of testimonials about Iranian assistance in Afghanistan are based more on wishful thinking than reality."
In a statement issued in response to Pace's comments, the Paris-based National Council of Resistance of Iran, a coalition of Iranian opposition groups, said Iran's Quds Force has been active in Afghanistan for several years.
Mohammad Mohaddessin, chairman of the Iranian group's foreign affairs committee, said: "Export of fundamentalism and terrorism to neighboring and Islamic countries has been one of the pillars of the clerical regime's foreign policy - something that the Iranian resistance has warned about for the past two decades."
The United States has about 25,000 troops in Afghanistan, mostly in the eastern area. The main focus of U.S. and Afghan government concern about arms and training for the Taliban is the largely ungoverned tribal area of Pakistan along the Afghan border, where the Taliban have found sanctuary. With regard to Iranian activities in Iraq, Pace said it is clear that Quds Force members are involved in the network that supplies materials to make roadside bombs, which are a leading killer of U.S. troops in Iraq. "We know that there are munitions that were made in Iran that are in Iraq and in Afghanistan," he said, adding that it also is clear that the Quds Force reports to the Iranian Revolutionary Guards, which reports directly to Iran's supreme leader, Ayatollah Ali Khamenei. "We surmise from that one of two things: Either the leadership of the country knows what their armed forces are doing, or they don't know. In either case, that's a problem," Pace said. He was asked what the U.S. government intended to do about Iranian military aid to forces opposing U.S. troops. "We will continue to be very aggressive inside of Iran - I'm sorry, excuse me, inside of Iraq - and inside of Afghanistan against any elements that are posing a threat to our own forces," he replied, adding that military action against Iran was not the first choice. "There is a lot more diplomacy, not only between the United States and Iran but between all the nations of the world and Iran, that can still be brought to bear to change Iran's attitude," he said. "Military force is your last tool, not your first tool," he said. "There are still many international tools available to address Iranian interference." AP-CS-04-17-07 1419EDT