Iranian Revolutionary Guard boats careered in an unprecedented and “unduly provocative” manner toward U.S. Navy vessels, according to a Pentagon report made public yesterday, just as President Bush was about to launch a trip to the Middle East, where he said he planned to warn the region’s leaders about the threat posed by Tehran.

Western analysts said the incident early Sunday might have been designed by leaders of the hawkish Revolutionary Guards to taunt the American military on the eve of Mr. Bush’s trip, reflecting growing internal tensions in Tehran between members of supreme leader Ayatollah Khamenei’s inner circle and a new generation of confrontation-oriented clerics around President Ahmadinejad.

In the first official response from Tehran, Iran’s Foreign Ministry spokesman, Mohammad-Ali Hosseini, confirmed the incident yesterday, telling the state-run Islamic Republic News Agency that it was “something normal that takes place every now and then.” But that was not the way it was viewed in Washington, where Pentagon officials vowed to continue America’s presence in the Persian Gulf despite the incident that reportedly involved five speeding Iranian boats that tried to intimidate three American vessels.

“America may not currently have the fire power in the Gulf to react militarily, but I doubt Iran will get away with this the way Britain allowed,” a Middle Eastern intelligence source said, speaking on condition of anonymity. He referred to the kidnapping in March 2007 of 15 British naval officers who were held for nearly two weeks before they were let go unharmed. There was no British retaliation at the time.

“The Revolutionary Guards wanted to create a confrontation where they believed the Americans were not ready for it,” added another Iran watcher, Israel Radio’s Farsi Service broadcaster, Menashe Amir. “From information I gathered observing Iran’s internal affairs, the provocation was not approved by Khamenei — but that does not mean Ahmadinejad did not know about it,” he added.

The five small “high-speed craft” approached the American vessels that were on a “routine transit” through the Hormuz Straits, entering the Gulf, said the Fifth Fleet Commander, Vice Admiral Kevin Cosgriff. The 30-minute incident in the first daylight hours Sunday took place “at least” 15 miles from Iranian territory and certainly beyond its 12-mile territorial waters, he said, identifying the American vessels as USS Port Royal, USS Hopper, and USS Ingraham.

The five Iranian boats “broke into two groups, one to one side of the formation, one to the other,” Mr. Cosgriff said, briefing Pentagon reporters yesterday via satellite. The boats, which in America’s assessment belonged to the Revolutionary Guards, “maneuvered aggressively in the direction of the U.S. ships,” he said.

At one point, the ships received “a radio call that was threatening in nature, to the effect” that “the U.S. ships would explode,” the admiral added, saying it was reminiscent of the 2000 suicide bombing of the USS Cole. “Subsequently, two of the Iranian boats were observed dropping objects in the water, generally in the path of the final ship in the formation, the USS Ingraham. These objects were white box-like objects that floated, and obviously the ship passed by them safely.”

Despite such behavior, which he deemed “unnecessary, without due regard for safety of navigation and unduly provocative,” and although radio calls from the “clearly marked” American vessels remained unheeded, the American ship commanders “did not believe they needed to fire warning shots,” Mr. Cosgriff said.

President Bush, who is due to arrive in Israel tomorrow to launch a regional trip, addressed growing Israeli concerns about Iran. “Part of the reason I’m going to the Middle East is to make it abundantly clear to nations in that part of the world that we view Iran as a threat,” Mr. Bush told Israel’s top selling newspaper, Yediot Achronot, adding that the recent assessment included in the National Intelligence Estimate “in no way lessens that threat, but in fact clarifies the threat.”

Iranian officials reacted with scorn to Mr. Bush, who made similar statements to Arab and other Israeli press outlets, stressing the need to tighten economic sanctions against Tehran. America’s attempts to break Iranian ties to Arab countries like Syria “are dreams and illusions,” said the former Iranian nuclear negotiator, Ali Larijani, speaking to reporters in Damascus Sunday.

Mr. Larijani was sent by Ayatollah Khamenei to Syria and Egypt to counter Mr. Bush’s trip, Mr. Amir said yesterday. But assigning such a high profile mission to him was also meant as an internal signal. A strong ally of the aging supreme leader, Mr. Larijani was recently pushed aside by Mr. Ahmadinejad, who is part of a group of politicians with ties to the Revolutionary Guards, who plan to contest Ayatollah Khamenei’s leadership by promoting hard line clerics as his replacement.

Meanwhile, as Iran’s air force is reportedly manufacturing a new generation of a stealth-type warplane, Admiral Cosgriff reported that two American F–18 Super Hornets collided yesterday in the northern Persian Gulf in an accident involving three pilots. The planes were lost but the American aviators “safely recovered aboard USS Harry S Truman in good condition,” he said.