The U.S. drone that apparently fell into Iran's hands was part of a joint CIA-military reconnaissance operation, Fox News has learned.
A senior U.S. official confirmed to Fox News that the spy plane was being used for the CIA-military operation along the Afghan-Iranian border when it lost connectivity and disappeared.
Officials had earlier confirmed the Iranians have the RQ-170 drone, but it was previously unclear what the drone was doing or which agency was operating it.
After Iran's military made the questionable claim Sunday that it had shot down the drone, the CIA at first referred questions to the Pentagon.
The NATO-led military coalition then issued a brief statement, appearing to describe the mission as part of the routine military operation in Afghanistan.
"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 International Security Assistance Force said. "The operators of the UAV lost control of the aircraft and had been working to determine its status."
But the official confirmation that the drone was part of a CIA-military mission would seem to line up with earlier confirmation that the drone was not a run-of-the-mill aircraft.
The RQ-170 Sentinel, which is so advanced that the U.S. Air Force has not even distributed a photo of it, is manufactured by Lockheed Martin and is equipped with stealth technology. The $6 million stealth aircraft has an RQ in its name to indicate it is unarmed.
The CIA's secret drone program is often used to fly missions over countries where the U.S. is not formally at war, such as Pakistan. It remains unclear what exactly this particular drone was doing in western Afghanistan.
Iran said Wednesday the drone was flying deep inside Iranian airspace when it was brought down by the country's armed forces.
Iranian state radio said the drone was detected over the eastern town of Kashmar, some 140 miles from the border with Afghanistan.
The report doesn't speculate as to why the drone flew over the town, located in an agricultural area famous for Persian carpets and saffron.
According to a senior U.S. military source with intimate knowledge of the Sentinel drone, the aircraft likely "wandered" into Iranian air space after losing contact with its handlers and is presumed to be intact since it is programmed to fly level and find a place to land, rather than crashing.
Neither the Air Force nor manufacturer Lockheed Martin has released much information about the plane, dubbed "The Beast of Kandahar" in 2007 when its existence was finally confirmed.
"This is a big prize in terms of technology," the senior U.S. military source told Fox News.
The spy plane uses the same stealth technology as the drone used to monitor the compound during the raid that killed Usama bin Laden, U.S. military sources told Fox News on Monday.
Amid the standoff, the Obama administration is trying to convince Congress not to proceed with a new sanctions proposal on Iran.
After the Senate voted unanimously last week to sanction Iran's Central Bank, the Obama administration warned that the sanctions could inadvertently increase oil prices and in turn benefit Iran. The administration urged Congress to water down the proposed penalties.
Fox News' Jennifer Griffin and The Associated Press contributed to this report.