U.S. Senator Joe Lieberman says he is skeptical about Iran’s claim that it is building a copy of an American drone that went down in Iran last year.

Lieberman, who chairs the Senate Homeland Security and Governmental Affairs Committee, told Fox News Sunday that he believes that Iran is blustering, as it is on the defensive because of the economic sanctions against it.

Lieberman added that he did not "have confidence at this point that Iran is really able to make a copy of the American drone."

However, the senator said he has not received a briefing from the U.S. government about the issue, noting it was not good for the U.S. when the drone went down.