Washington: Five Iranian Revolutionary Guard boats harassed and provoked three US Navy ships in the Strait of Hormuz, a major oil shipping route off the Iranian coast, over the weekend.

The captain of one US vessel was in the process of giving the order to shoot when the Iranian ships began turning away, CNN said.

A radio transmission from one of the Iranian ships said, "I am coming at you. You will explode in a couple of minutes," CNN reported, citing a US official.

After the threatening radio communication, US sailors manned their ships' guns and were very close to opening fire,it said.

Iran's Revolutionary Guards said that its high-speed boats never threatened the U.S. 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.

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

"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," Cosgriff told The Associated Press in a telephone interview Tuesday.

The U.S. commander also said 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," Cosgriff said.