An Iranian fighter jet tried to intercept a US Predator drone over the Persian Gulf but backed off after encountering two US military aircraft, the Pentagon says.

No shots were fired in the confrontation on Wednesday, officials said, but the United States renewed a vow that it would protect its forces in the region.

The Pentagon initially said one of the US aircraft discharged a flare as a warning to the Iranian plane but officials later said no flare was let off.

The incident, which the Pentagon said took place over "international waters," highlighted the tensions between the two arch-foes and the risks of an accidental clash escalating into a serious crisis.

At one point the Iranian F-4, an old US-built warplane dating from the Vietnam War era, was within 25 kilometers of the unmanned Predator drone, spokesman George Little said.

The unarmed Predator, the workhorse of the US fleet of robotic planes, was carrying out "a routine classified surveillance flight" over the Gulf when it was approached by the Iranian warplane, he said in a statement.

In November, an Iranian fighter jet fired at a Predator plane, provoking a strongly-worded protest from the United States.

As after the November incident, the Pentagon warned it would keep up surveillance flights over what it deems international waters and to safeguard US forces in the region...

The US expanded its military presence around the Gulf over the past year, deploying minesweepers and F-22 fighters to the area.

This came after Iran threatened to block the strategic Strait of Hormuz in retaliation for tough international sanctions imposed over its nuclear program.

READ FULL SOURCE ARTICLE: 03/14/2013