The US military has released video and audio recordings of Iranian boats that it says threatened to blow up US Navy vessels in the Strait of Hormuz.
The jerky footage, shot from one of the three US ships, shows several small boats approaching at high speed.
US President George W Bush described the stand-off as "provocative", adding that it was a "dangerous situation" that should not have happened.
Iran has dismissed the incident as a "routine" encounter.
The video, which was shot from the bridge of the USS Hopper, appears to show the small boats racing near the wake of the US ships and crossing close to each other.
One boat is shown in close-up - a blue speedboat with at least two crew.
After spotting the approaching vessels, a Navy crewman can be heard over the radio, warning them they are approaching a coalition warship.
"Request you establish communications, identify yourself and state your intentions, over," he says.
He refers to "five unidentified small surface" boats, and the ships' sirens can be heard in the background.
The four-minute video condenses what US officials have described as a 20-minute stand-off.
At the end of the US recording, the screen goes black and the remainder is in audio only. Some of the communication is unclear.
The US issues a final warning that if the boats do not change course immediately they will be "subject to defensive measures".
A heavily-accented male voice can be heard saying: "I am coming at you. You will explode."
The Pentagon has said this threat was issued by the Iranian boats.
The speedboats, believed to belong to Iran's Revolutionary Guards, came within about 200m (650ft) of the US vessels, Pentagon officials said.
The weekend stand-off happened in a major oil shipping route, in what the Pentagon insists were international waters.
Mr Bush said: "I don't know what their thinking was, but I'm telling you what I think it was, I think it was a provocative act."
The US president was speaking in the White House Rose Garden on the first anniversary of the Iraq troop surge, hours before leaving for a week-long Middle East trip.
During his first visit to Israel as president, Mr Bush hopes to push forward Israeli-Palestinian peace talks relaunched in Annapolis late last year.
The BBC's Richard Lister in Washington says it seems the US does not want to make too much of the incident for fear it will overshadow his visit to the region.
Iran has played down the event, calling it an "ordinary occurrence".
An Iranian foreign ministry spokesman said: "This... happens for the two sides every once in a while and, after the identification of the two sides, the issue is resolved."