Boasts by Tehran Sunday to have reverse-engineered a CIA spy drone were dismissed hours later by influential US Senator Joe Lieberman as "Iranian bluster."
Lieberman told "Fox News Sunday" he felt "skepticism" after an Iranian military commander said the Islamic republic was building a copy of the drone, which came down on Iranian soil in December 2011.
"There is some history here of Iranian bluster particularly now when they're on the defensive because of our economic sanctions against them," said Lieberman, an independent who chairs the Senate Homeland Security Committee.
Iranian General Amir Ali Hajizadeh, head of the elite Revolutionary Guards' aerospatial division, claimed on state television that a duplicate was under construction after scientists succeeded in "penetrating the drone's secrets."
US officials have admitted that the unmanned, bat-winged RQ-170 Sentinel drone went down four months ago during a CIA mission over Iran, citing a technical problem.
US President Barack Obama made a vain request for Iran to return the drone, although Defense Secretary Leon Panetta indicated there was little technological knowledge to be gleaned from it.
The drone was displayed on state television by a gleeful Iranian military in the days after its retrieval. It appeared to be intact with some damage to one of its wings.
Iran says one of its cyberwarfare team managed to hack into its controls by confusing the aircraft's highly-sophisticated GPS navigation system.
The drone claim comes against the backdrop of spiraling international tension over Iran's suspect nuclear program. Iran denies Western assertions that it is trying to produce an atomic weapon.
The standoff intensifies with every passing month as Israel -- which Iranian leaders have repeatedly vowed to destroy -- expresses growing impatience.
The United States does not believe Iran has so far taken a decision to develop a nuclear weapon, or that the time is right for military action, preferring to give international sanctions time to work.
But there is growing speculation that Israel could take a unilateral decision to launch pre-emptive air strikes on Iranian nuclear sites.
In Istanbul last weekend, Iranian officials sat down with diplomats from major powers to seek a resolution to the nuclear standoff. Both sides agreed to hold a more in-depth meeting in Baghdad on May 23.