WASHINGTON - The United States on Thursday lodged a formal diplomatic protest with Iran over an incident last weekend in which Iranian speedboats harassed U.S. warships in the Persian Gulf.

The protest repeats U.S. complaints about Sunday's "provocative" action in the Strait of Hormuz and was sent to the Iranian Foreign Ministry via the Swiss Embassy in Tehran, which represents U.S. interests in Iran, the State Department said.

"It reiterates the points that we have made publicly in the last few days," deputy spokesman Tom Casey told reporters. "We certainly don't want to see the Iranians taking any kind of provocative actions or provocative steps against our ships or against any ships that are transiting what is a primary international waterway."

In Tehran, Iranian Foreign Ministry officials said they were unaware of the U.S. protest.

At a Pentagon news conference, Defense Secretary Robert Gates said the Iranian boats had acted "in a pretty aggressive manner."

"What concerned us was first the fact that there were five of these boats and, second, that they came as close as they did to our ships and behaved in a pretty aggressive manner," he said.

The Bush administration had been considering the move for several days, debating whether a formal protest would have any impact on Iranian behavior, given numerous strong public comments about the incident already delivered by the president and his top aides, according to officials familiar with the discussion.

They said the decision to proceed with the protest was made after consensus was reached to back up and reinforce those comments with a formal diplomatic demarche, or communication.

In his remarks, Casey dismissed Iranian claims that there was nothing unusual about the incident as well as a videotape aired by Iranian television on Thursday that appeared to be an attempt to show there had not been a confrontation between the vessels.

"We all understand what happened in this incident," he said.

The Pentagon maintains that Iranian naval speedboats swarmed around U.S. warships in a threatening manner and released its own video of the incident in which a man in accented English says, "I am coming to you. ... You will explode after ... minutes."

In Israel on Wednesday, Bush warned Iran not to repeat such actions, which he said would draw "serious consequences."

Iran denies its boats threatened the U.S. vessels, and accused Washington of fabricating its video. The Pentagon has dismissed that claim and warned that its ships would respond with force if threatened.

The grainy 5-minute, 20-second Iranian video shows a man speaking into a handheld radio, with three U.S. ships floating in the distance. It appeared to be shot from a small boat bobbing at least 100 yards from the American warships. But the footage does not show any Iranian boats approaching the U.S. vessels or any provocation.

The entire incident lasted about 20 minutes, according to the U.S. Navy, and a Pentagon official said that while the Iranian video appeared to have been taken around the time of the confrontation, controversial parts had been edited out.

The clip aired on Iran's state-run English-language channel Press TV, whose signal is often blocked inside Iran. It also aired on the state-run Al-Alam Arabic channel, with an announcer saying the video showed "a routine and regular measure."

The incident, which ended without any shots fired, has heightened U.S.-Iranian tension as Bush visits the region. Bush was in the West Bank on Thursday, and heads next to Arab nations where he is expected to discuss strategy on Iran.

The confrontation has handed his administration new ammunition in its battle to convince allies that the Tehran government remains a threat, despite a U.S. intelligence report last month saying Iran abandoned a secret nuclear weapons program in 2003. Iran denies seeking nuclear weapons, saying its program is meant to produce energy.

Mohamed ElBaradei, who heads the U.N.'s International Atomic Energy Agency, is visiting Iran this week to discuss Iranian compliance with international demands, including halting its uranium enrichment and reprocessing activities.

Casey said it was important for ElBaradei to try to convince the Iranians to meet those demands, but stressed Washington had no great hopes the visit would accomplish that end.

"To the extent that his trip can get the Iranians to provide any answers -- which, of course, they were free to provide, could have provided and should have provided years ago -- that's a positive thing," he said.

"I don't think we have any particular expectation that all those answers will be forthcoming," Casey added.