A U.S. official said Sunday that Washington had no indication that a drone that had crashed in Iran had actually been shot down.
In Tehran, state television quoted a military source as saying that Iran's military had shot down a U.S. reconnaissance drone aircraft in eastern Iran.
"There is absolutely no indication up to this point that Iranians shot down this drone," the official told NBC News.
The NATO-led force in Afghanistan said the drone the Iranians claim to have shot down may be an unarmed surveillance drone that was lost last week while flying over western Afghanistan. A surveillance drone flying over western Afghanistan had gone out of control late last week and may be the one Iran said it had shot down over its own airspace, the International Security Assistance Force (ISAF) said on Sunday.
"The UAV to which the Iranians are referring may be a U.S. unarmed reconnaissance aircraft that had been flying a mission over western Afghanistan late last week. The operators of the UAV lost control of the aircraft and had been working to determine its status," an ISAF statement said.
The statement about the unmanned aerial vehicle (UAV) was issued in Kabul and released to reporters covering an international conference on Afghanistan in the German city Bonn. Iran's armed forces have shot down an unmanned U.S. spy plane that violated Iranian airspace along the country's eastern border, the official IRNA news agency reported Sunday.
Iran is locked in a dispute with the U.S. and its allies over Tehran's disputed nuclear program, which the West believes is aimed at developing nuclear weapons. Iran denies the accusations, saying its nuclear program is entirely peaceful and that it seeks to generate electricity and produce isotopes to treat medical patients.
The type of aircraft Iran says it downed, an RQ-170 Sentinel, is made by Lockheed Martin and was reportedly used to keep watch on Osama bin Laden's compound in Pakistan as the raid that killed him was taking place earlier this year.
The surveillance aircraft is equipped with stealth technology, but the U.S. Air Force has not made public any specifics about the drone.
Iran said in January that two pilotless spy planes it had shot down over its airspace were operated by the United States and offered to put them on public display.
The Islamic Republic holds frequent military drills, primarily to assert an ability to defend against a potential U.S. or Israeli attack on its nuclear facilities.
Tehran has focused part of its military strategy on producing drones for reconnaissance and attacking purposes.
Iran announced three years ago it had built an unmanned aircraft with a range of more than 600 miles (1,000 kilometers), far enough to reach Israel.
Ahmadinejad unveiled Iran's first domestically built unmanned bomber aircraft in August 2010, calling it an "ambassador of death" to Iran's enemies.