Iran claimed that it had reverse-engineered a US spy drone captured by its armed forces last year, and that it had been building a copy. It cited as proof details of the aircraft's history, which, it said, included a surveillance mission over the home of Osama bin Laden in Pakistan just two weeks before he was killed.
The US dismissed the claim as "bluster", but it would be an embarrassment for the US military and intelligence community if Iran was able to produce a replica.
After the loss of the drone in December, the US claimed there was little in the software that could be exploited for intelligence purposes and that it was in any case encrypted.
The commander of the Islamic Revolutionary Guard Corps, Brigadier General Amir Ali Hajizadeh, told the Iranian Fars news agency that they had succeeded in reverse-engineering the drone.
A spokesman for the CIA, which operates the drones, declined to comment. The drones have been used for monitoring and assassinating suspected terrorists in Pakistan and for intelligence-gathering in Iran, mainly of its nuclear sites.
The US blamed the loss of the RQ-170 Sentinel drone on a technical problem. Iran claims it brought it down electronically, by disrupting its GPS system. President Barack Obama asked for the device to be returned, a request that Iran rejected. The former vice-president, Dick Cheney, criticised Obama for failing to take a more robust approach, such as destroying the drone on the ground before the Iranians could get to it.
Joe Lieberman, chairman of the Senate homeland security committee, who receives regular intelligence updates, told Fox News on Sunday that he was sceptical about Hajizadeh's claims: "There is some history here of Iranian bluster, particularly now when they're on the defensive because of our economic sanctions against them.
"Look, it was not good for the US when the drone went down in Iran, and not good when the Iranians grabbed it. [But] I don't have confidence at this point that they are really able to make a copy of it. It's a very sophisticated piece of machinery and has served our national security well, including, I would guess, being used to look all over Iran, particularly at areas where we have reason to believe that they are working on a nuclear weapon."
In support of his claim to have penetrated the drone's secrets, Hajizadeh said Iranian engineers had successfully retrieved information from the aircraft's memory. As a result, he said, they knew that it had flown a surveillance mission over Osama bin Laden's Pakistan hideout two weeks before he was killed, and that drone parts had been sent to California for work in October 2010 before the drone was transferred to Kandahar, in Afghanistan. The drone then experienced technical problems during operations from Kandahar and was sent back to the US, to Los Angeles, for tests on its sensors and other parts.
"Had we not accessed the plane's software and hard disk, we wouldn't have been able to uncover these facts," Hajizadeh said.
Although the US insisted in December that the drone carried little useful intelligence, concern was expressed about reverse-engineering of its radar-deflecting paint coating and special optics used for spying.
Hajizadeh's claim was made against a backdrop of international tension over western suspicion that Tehran is seeking nuclear weapons capability. Israel has issued repeated threats that it will bomb Iran's nuclear installations rather than allow it to obtain a nuclear bomb.
Iran engaged in diplomatic negotiations in Istanbul earlier this month and a further round is scheduled for 23 May in Baghdad.