CAIRO — President Bush today described a confrontation between Iranian boats and U.S. Navy vessels in the Strait of Hormuz as a “provocative act.”

The top Navy commander in the Middle East, Vice Admiral Kevin Cosgriff, disputed Iranian claims that the incident early Sunday was a routine encounter, saying Iran’s “provocative” actions were “deadly serious” to the American military.

“It was a dangerous situation,” Mr. Bush told reporters at the White House. “They should not have done it, clear and simple. I don’t know what their thinking was, but I’m telling you what my thinking was. I think it was a provocative act.”

The confrontation was an unusual flare-up of American-Iranian tensions in the Persian Gulf as Mr. Bush begins his first visit to the Middle East. In the tour, Mr. Bush is to visit Saudi Arabia and other Gulf Arab allies, in part to coordinate in confronting Iran.

Many Arab countries fear the Iranian-American rivalry could erupt into a military confrontation that would put them in the crossfire and hurt vital Gulf oil traffic.

Iran’s Revolutionary Guards said that its high-speed boats never threatened the American vessels during the encounter, insisting it only asked them to identify themselves, then let them continue into the Gulf. A Guards commander defended his force’s right to identify ships in the sensitive waterway.

Admiral Cosgriff, the commander of U.S. 5th Fleet, which patrols the Gulf and is based in nearby Bahrain, said the American vessels had already been identified by Iranian authorities earlier in the day before the confrontation occurred.

“The group had been successfully queried by an Iranian ship, possibly a Revolutionary Guards ship, and two or three Iranian (shore) stations and an Omani station,” Admiral Cosgriff said.

The American commander also pointed out that the American ships were clearly marked and the incident took place during the day when they could be seen. “I can’t help but conclude that it was provocative,” Admiral Cosgriff said.

“There is video” of the incident, Admiral Cosgriff said. “We’re using it as part of our assessment. That will be made available in due course, as well as the audio.”

The White House echoed Admiral Cosgriff’s characterization today, calling Iran’s actions “reckless.”

“It was not normal behavior,” a White House spokeswoman, Dana Perino, said. “It’s just another point of reference for people in the region who are concerned about the behavior of Iran.”

The Pentagon has said the American ships were on the verge of opening fire on the Iranian boats when they fled.

Admiral Cosgriff said the five Iranian boats, outfitted with outboard motors and carrying three to four people each, rapidly approached three American warships — cruiser USS Port Royal, destroyer USS Hopper, and frigate USS Ingraham, which were passing through the Strait into the Gulf.

Two of the Iranian boats went to the ship’s left side, three to the right, he said. The two on the left “were more energetic and made a number of runs toward the lead ship, the USS Hopper.”

As the two boats did so, the USS Hopper’s crew heard a radio call threatening that the American ships would “explode.” The two boats dumped boxes into the water.

However, American military officials, including Admiral Cosgriff, said they have not been able to definitively connect the radio call with one of the Revolutionary Guards boats.

“The ships were close enough to shore that the call could have come from a shore station, it could have come from another boat,” the 5th Fleet spokeswoman, Commander Lydia Robertson, said. “But the call did happen while the small boats were there.”

Iran’s Foreign Ministry called the incident a “normal” encounter between the two countries’ ships and said it had been resolved.

“No threatening messages were exchanged,” state television quoted an unidentified Iranian Revolutionary Guards official as saying today.

A senior Revolutionary Guards commander, Ali Reza Tangsiri, said Iran had the right to ask any ships to identify themselves upon entering or leaving the Persian Gulf.

“It is a basic responsibility of patrolling units of the Revolutionary Guards to take necessary interception measures toward any vessels entering into the waters of the Persian Gulf,” Commander Tangsiri said, according to the Mehr news agency.

Admiral Cosgriff objected to Iranian attempts to downplay the incident, saying, “This is deadly serious to me.”

“I hope from this lesson they realize that we are concerned by small, high-speed vessels,” Admiral Cosgriff said. I hope they understand we will take those actions we deem appropriate to defend our ships and our sailors.”

A Dubai-based analyst with the Institute for Near East and Gulf Military Analysis, Riad Kahwaji, said Iran may have been seeking to send a “political message” to Arab Gulf states to highlight the dangers of military confrontation.

“When somebody gets so close to a big ship then he’s very likely asking for trouble or trying to provoke something,” he said. “Opening fire means sparking a war … Does anyone really want to take that risk?”