U.S. officials are challenging Iran's claims that it has reverse-engineered the American drone that went down last year inside its borders -- though one source raised concern that Tehran could try to break down the drone's components and offer access to China and Russia. 

The drone's coating, which resists detection by radar, is a high priority to the Chinese, who also sought access to a stealth U.S. helicopter tail from Pakistan after the Usama bin Laden raid. 

A former intelligence official told Fox News it's unlikely the Iranians could figure out how to recreate the drone, and that the pressing concern would be to try to use the technology to bargain with the Chinese or the Russians. 

While China does not necessarily have the technology to help significantly advance Iran's nuclear program in exchange for access to drone parts, China could offer Iran an IOU of sorts -- for a favor like a veto at the U.N. Security Council, the former official said. 

The Russians would also be interested in any U.S. intelligence collection capability, and could offer Iran ballistics technology useful for a nuclear delivery system. 

Still, the former official described any information the Iranians have been able to glean about the drone's reconnaissance history as "low-hanging fruit," since it would be contained in the drone's equivalent of a black box. 

Speaking on "Fox News Sunday," Sen. Joe Lieberman, I-Conn., also said he takes the Iranian pronouncements with "skepticism." 

"I think there is a history here of Iranian bluster, particularly now when they are on the defensive because of our economic sanctions against them," Lieberman said. "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." 

As for Iranian claims they have broken the codes or encryption, the claims were described to Fox News as a stretch because the encryption "keys" are changed on a monthly basis, and sometimes even more frequently than that. 

"The Iranians are pulling data down, intercepting data all the time, but they can't decode it," the former intelligence official said. 

A 10-week investigation into the downing of the CIA drone in Iran, completed in February, raised  questions as to whether the malfunctions inadvertently may have handed the Iranians not only the aircraft but its data. 

Based on the review, Fox News was told that investigators think one of the drone's three major "data streams" began sending back bad information to its U.S.-based operator. A leading question is whether the bad data caused the drone's operator to inadvertently land the aircraft. But it also raises the possibility that the faulty data stream could have prevented the drone from dumping the intelligence it had collected. When a drone malfunctions, it is programmed to dump data so it does not fall into the wrong hands. 

Fox News was told in February that the CIA's comprehensive review has been unable to replicate the specific malfunction that brought down the drone in Iran. Contact was lost with the drone and its operators on Nov. 29. 

A congressional official, also familiar with the CIA review, said: "We have looked at this eight ways to Sunday. I can tell you it was a U.S. technical problem. The (data) was not lining up and it was not the result of Iranian interference or jamming." 

While efforts to reproduce or replicate the malfunction have failed, investigators are now focusing on how to prevent a repeat in the future -- but without the hardware or the drone itself, those efforts have been challenging. 

A CIA spokesman declined to comment.