The U.S. Navy said Friday that one of its ships fired warning shots at a small Iranian boat in the Strait of Hormuz in December during one of two serious encounters that month.
The USS Whidbey Island fired the warning shots on Dec. 19 in response to a small Iranian boat that was rapidly approaching it, said a U.S. Navy official.
"One small (Iranian) craft was coming toward it, and it stopped after the Whidbey Island fired warning shots," said the official, speaking on condition of anonymity because of the sensitivity of the issue.
It was the first official confirmation that the United States had fired warning shots in any recent confrontation with Iran in the Gulf.
In the second incident that month, the USS Carr encountered three small Iranian craft on Dec. 22, two of which were armed, said the official. The USS Carr did not fire warning shots, but sent warning blasts on the ship's whistle, which caused the boats to turn around.
Diplomatic protest lodged in another incident
The reports come a day after the United States lodged a formal diplomatic protest with Iran over an incident Sunday in which Iranian speedboats harassed U.S. warships in the Persian Gulf.
Adm. William J. Fallon, the top U.S. military commander in the Mideast, said Friday that Iran runs the risk of triggering an unintended conflict if its boats continue to harass U.S. warships in the strait.
And Navy Adm. Mike Mullen, chairman of the U.S. military's Joint Chiefs of Staff, said Friday that the United States is ready to counter any threat.
"The incident ought to remind us all just how real is the threat posed by Iran and just how ready we are to meet that threat if it comes to it," Mullen told reporters.
"We will defend ourselves and our ships, and we will do so with deadly force if need be," he said at the Pentagon.
Latest incident in Persian Gulf
Five Iranian speedboats maneuvered aggressively close to three U.S. Navy ships in the Strait of Hormuz on Sunday, as the U.S. ships received a radio transmission threatening an explosion, according to the United States.
The United States released its complete 35-minute video of the incident, but it contained little new from the 4-minute edited version released earlier this week.
The United States has formally complained about the incident. But Iranian officials have dismissed U.S. objections, saying the encounter was normal and the Iranian boats were merely trying to identify the U.S. vessels.
The incident was another sign of tension between the United States and Iran, at odds over a range of issues including Tehran's nuclear program and its alleged role in Iraq.
The Strait of Hormuz is the most prominent potential "choke point" for crude oil flows, handling 17 million barrels per day, or two-fifths of globally traded oil.
Close to opening fire
U.S. officials have said U.S. sailors were close to opening fire Sunday before the Iranian boats moved away. They have said they believe the boats came from Iran's Revolutionary Guard Corps.
"I'd much rather prevent a war than fight one," Mullen said. "We'd all prefer Iran to take a more productive, positive role in the region. And I support the use of economic and diplomatic measures to help bring that about."
"But our own military restraint in dealing with that problem should in turn never be confused for a lack of capability."
Some U.S. commentators have suggested the U.S. sailors should have opened fire and their restraint will be interpreted by Iran as a sign of weakness. But Mullen, a former head of the U.S. Navy, said the crews' actions had been "exactly right."
Sides release videos, conflicting accounts
Both the United States and Iran have issued video footage to support their conflicting accounts of the incident.
The United States has also released the recording of a message it says was received by one of the U.S. ships. "You will explode after... minutes," a heavily accented voice on the recording says.
U.S. officials initially said the audio was believed to have come from one of the Iranian boats but they have since said they are not certain of its exact origin.
"I can't shed any light as far as the radio transmission is concerned," Mullen said. "If you're out there on the bridge, it's hard to tell where (radio transmissions are) coming from."
Tehran's strategy shift
The recent confrontation in the Persian Gulf reflects a strategy shift by Tehran to use its Revolutionary Guard's fast boats more aggressively in the region, Mullen said.
Mullen said the U.S. has been focused "for several years" on this shift to greater use of small, fast boats by the Iranian Revolutionary Guard Corps, which has taken over patrols in the Gulf from Tehran's regular navy.
"It's clearly strategically where the Iranian military has gone," said Mullen. "There's a projection they were going to do that over a number of years ... That was a big concern to me because of the history and the background with the (Revolutionary Guard). This fits that mold, as far as I was concerned."