WASHINGTON: The Pentagon revealed Thursday that two Iranian fighter jets fired on an unarmed US Predator drone in the Gulf last week but the aircraft was not hit, in an incident that underscored tensions in the region.

The incident occurred on November 1, less than a week before America’s presidential election, but the Pentagon kept it quiet until reports of the confrontation leaked out.

“They intercepted the aircraft and fired multiple rounds,” spokesman George Little told a news conference.

The Su-25 Frogfoot fighters, much faster than the slow-moving turboprop drone, fired at least twice and made two passes, he said.

It was unclear whether the Iranians intended to warn off the unmanned drone but Little said: “Our working assumption is that they fired to take it down.”

The confrontation threatened to derail diplomatic efforts to defuse a mounting crisis over Tehran’s nuclear program, amid a shadow war of cyberattacks, bombings and assassinations.

Tough new sanctions led by Washington are squeezing Iran’s economy, while the United States and Israel are accused of staging cyber sabotage on Tehran’s uranium enrichment plants.

The US military drone was “never in Iranian air space” and came under fire from the fighter jets off the Iranian coast over international waters, Little said.

The robotic Predator aircraft was conducting “routine surveillance” and the United States has told Iran it has no plans to suspend the flights, he said.

“The United States has communicated to the Iranians that we will continue to conduct surveillance flights over international waters over the Arabian Gulf consistent with longstanding practice and our commitment to the security of the region,” he said.

In a warning to Tehran, the Pentagon spokesman said the United States was prepared to safeguard its forces.

“We have a wide range of options, from diplomatic to military, to protect our military assets and our forces in the region and will do so when necessary,” Little said.

The MQ-1 drone was pursued further by the Iranian warplanes but was not fired on again, he said.

The Predator later returned safely to an unspecified military base in the region following the incident that occurred at 4:50 am US eastern standard time (0850 GMT).

The Predator, known as the weapon of choice in America’s bombing campaign against al Qaeda in Pakistan, was intercepted about 16 nautical miles off the Iranian coast, beyond the Islamic Republic’s territorial waters that extend 12 nautical miles off the country’s shore.

Iranian military speedboats have sometimes swarmed US warships in the Gulf and the strategic Strait of Hormuz, a vital waterway for the world's oil, but the incident last week was the first involving an American drone in a confrontation with Iranian aircraft, officials said.

Tensions over Iran’s nuclear ambitions prompted the United States to bolster its military presence around the Gulf over the past year, deploying two aircraft carrier battle groups in the area at all times, a squadron of stealthy F-22 fighters to the United Arab Emirates and more minesweeper ships.

With America’s drawn out election campaign finally over, analysts had predicted President Barack Obama might have more leeway to pursue diplomacy with Iran. But the encounter with the Iranian fighter jets served as a reminder that a single incident or misunderstanding could trigger conflict.

A new round of talks between Iran and six world powers, the first since June, is expected by the end of the year or in early 2013.

Iran insists its nuclear program is peaceful and has made clear any deal with the major powers has to offer relief from crippling sanctions.

Israel meanwhile maintains time is running out as Iran expands its uranium enrichment work, with Prime Minister Benjamin Netanyahu suggesting his country may stage a unilateral strike next year if Tehran continues on its present course.

At the State Department, officials unveiled yet more sanctions on Iran, targeting the communications minister and the culture ministry among others for censoring the media and the Internet.