The video, released by the U.S. Department of Defense on Tuesday, shows three motorboats approaching U.S. warships in the Strait of Hormuz.
"The video released by the U.S. Navy has been compiled of archive video files, and the sound has been fabricated," the Iranian Press TV quoted the unnamed Revolution Guards official as saying.
An audio recording features a voice from a U.S. ship telling one craft it was "straying into danger and may be subject to defensive measures". The small craft responded: "You will explode after a few minutes," according to Reuters.
The Iranian Foreign Ministry spokesman, Mohammad Ali Hosseini, played down the incident, saying that similar events occurred "every once in a while and, after the identification of the two sides, the issue is resolved."
Associated Press quoted a senior U.S. official as saying on Wednesday that any new naval crisis like this would have far more serious consequences.
"This was a very provocative act by the Iranians and could have and came very close to resulting in an altercation between our forces and their forces," Stephen Hadley, the U.S. national security adviser, told AP.
U.S. Secretary of State Condoleezza Rice called the Iranian action "provocative and dangerous" on Monday.
Tensions remain high between the U.S. and Iran over the Islamic Republic's nuclear program, despite the release of a report by the U.S. intelligence community in December 2007 stating that Iran was not seeking to build nuclear weapons.
