WASHINGTON  Just hours before President Bush began his trip to the Middle East, he sharply criticized Iran on Tuesday for fomenting “a dangerous situation” in an incident over the weekend in the Strait of Hormuz in the Persian Gulf.

Asked whether he thought the Iranians were trying to provoke a fight with the United States by having several of their vessels confront American craft, the president said the Iranians had engaged in “a provocative act.”

“It is a dangerous situation, and they should not have done it, pure and simple,” Mr. Bush said in a brief question-and-answer session in the Rose Garden. “I don’t know what their thinking was, but I’m telling you what I think it was.”

Although Iranian officials have played down the encounter, Bush administration officials see the timing as no coincidence. They have said that Iran was trying to provoke the United States just before the president’s weeklong trip to the Middle East. The president said pointedly on Tuesday that he would use the journey to remind America’s friends and allies in the region that Iran poses a danger.