(CNN) -- Iran has denounced video and audio recordings released by the United States of the two nations' confrontation in the Strait of Hormuz as "fabricated," according to statements carried by state-run television station.

Iranian Revolutionary Guard boats "harassed and provoked" U.S. Navy ships Sunday, the U.S. military says.

However, President George W. Bush repeated his assertion that Iran is "a threat to world peace" and warned the Islamic republic against any escalation.

"We have made it very clear, and they know our position, and that is: There will be serious consequences if they attack our ships," Bush said on Wednesday. "My advice to them is: Don't do it."

Iran's Foreign Ministry spokesman downplayed the incident earlier Wednesday, calling it "normal," state-run news agency IRNA reported.

"The case ... was similar to the past ones and it was a regular and natural issue," Mohammad-Ali Hosseini said, IRNA reported.

And the state-run Press TV quoted a spokesman for Iran's Revolutionary Guard Navy as saying that the video "had been compiled using file pictures and the audio had been fabricated."

The Pentagon Tuesday released a four-minute, 20-second video of Sunday's incident, including video showing small Iranian boats swarming around U.S. warships in the Persian Gulf. In the audio recording, a man speaking in heavily accented English threatened, "I am coming to you. ...You will explode after ... minutes." Watch the confrontation »

National Security Advisor Stephen Hadley warned Wednesday: "It's the kind of incident that can provoke exchange of fire. And we think the Iranians need to be on notice that they are fishing in troubled waters here."

Hadley, speaking to reporters aboard Air Force One as they flew with U.S. President George W Bush to Israel, said "it almost involved an exchange of fire between our forces and Iranian forces," but he stopped short of saying if the U.S. Navy would have fired the first shots.

"This is not -- this is a provocative act, not a smart thing to do, and they're going to have to take responsibility for the consequences if they do it again," Hadley said.

Bush called the confrontation "a provocative act" during a news conference in the White House Rose Garden Tuesday. "It's a dangerous situation, and they should not have done it, pure and simple," Bush said. "I don't know what their thinking was."

The U.S. had called the incident, between five Iranian Revolutionary Guard boats and three U.S. Navy ships as a "significant" confrontation in which the U.S. boats had been "harassed and provoked."

An Iranian official, however, said it was not a serious incident, the state-run news agency IRNA reported.

U.S. military officials said the confrontation, between five Iranian Revolutionary Guard boats and three U.S. Navy, occurred early Sunday morning in the Strait of Hormuz, a narrow shipping channel leading in and out of the Persian Gulf.

The Pentagon said that as the guided missile destroyer USS Hopper, the guided missile cruiser USS Port Royal and the guided-missile frigate USS Ingraham were entering the Persian Gulf, five Iranian boats approached them at high speed and swarmed them.

The Iranian boats made "threatening" moves toward the U.S. ships and in one case came within 200 yards of one of them, the U.S. officials said.

An audio recording has an unidentified Navy crew member say over the radio: "This is coalition warship. I am engaged in transit passage in accordance with international law. I intend no harm. Over."

The boats continue to race through the water even as the U.S. warship repeatedly sounded its horns.

"I am coming to you," a deep, thickly accented voice says in English over the radio.

To that, an unidentified sailor aboard the Hopper, speaking into a radio, asks the boats to identify themselves and steer clear.

"Inbound small craft: You are approaching a coalition warship operating in international waters. Your identity is not known; your intentions are unclear," he says.

"You may be subject to defensive measures. Request that you establish communications now or alter your course immediately to remain clear."

Immediately afterward, the same deep voice says: "You will explode in a few minutes."

When the U.S. ships heard that radio transmission, they took up their gun positions and officers were "in the process" of giving the order to fire when the Iranians abruptly turned away, U.S. officials added.

After the radio transmission, one of the Iranian boats dropped white boxes into the water in front of the U.S. ships, the officials said. It was not clear what was in the boxes, officials said, and they were not picked up because it was not known what they were . No shots were fired, and no one was injured.

It was not clear, however, that the voice was coming from any of the boats, Cdr. Lydia Robertson, the 5th Fleet spokeswoman in Bahrain, told CNN. It could have come from another ship in the area or from shore, she said. "We don't have a direct connection, but it's not necessarily a disconnect," she said.

In November the U.S. military reported that Iran's Revolutionary Guard Corps -- which the United States considers to be a major supporter of terrorist activity -- had taken command of Tehran's naval operations in the Persian Gulf, one of the world's key shipping regions and an area of high tension.

In March last year, Iran detained 15 crew members of a British ship before releasing them after nearly two weeks. Iran alleged the British vessel strayed into Iranian waters -- an assertion Britain strongly denied. E-mail to a friend