WASHINGTON — Iranian warplanes fired at an unmanned US military surveillance drone in international airspace over the Persian Gulf last week, Pentagon officials disclosed Thursday, saying that while the aircraft was not hit, Washington made a strong protest to Tehran.
The shooting, which the Pentagon said occurred Nov. 1 — five days before the US presidential election — was the first known instance of Iranian warplanes firing on a US drone.
George Little, the top Pentagon spokesman, attributed the weeklong silence on the incident to restrictions on discussing classified surveillance missions. But it doubtless will raise questions about whether that silence had been meant to forestall an international controversy before the election.
Little discussed the episode during a Pentagon news conference only after the shooting had been disclosed by news organizations.
A senior administration official sought to tamp down the ripple effects of the episode, noting that it should not be viewed as a precursor to a broader military confrontation or as something that would derail potential diplomatic contacts between the United States and Iran over its disputed nuclear program. ‘‘We view it as another data point in what is clearly more aggressive tactics on the part of the Iranians,’’ the senior official said.
Severe tensions between the United States and Iran, principally over the nuclear program, have led to heavy sanctions on Iran that have deeply afflicted the country’s economy — most notably its ability to do international financial transactions and to sell oil, the most important Iranian export. Further sanctions were announced Thursday by Treasury and State Department officials.
At the same time, there has been some optimism that President Obama, elected to a second term, might have some new political leverage to negotiate with Iran over the nuclear program, which the Iranians say is meant for peaceful purposes. The United States and Israel have called the program a guise to create the ability to make nuclear weapons.
There was no immediate comment from Iran on the Pentagon’s disclosure.
Little said Iranian warplanes ‘‘fired multiple rounds’’ but missed the drone, a Predator, which has a unique silhouette similar to a giant, upside-down flying spoon and is not easily confused with a piloted jet fighter.
Officials declined to speculate about whether the Iranian pilots were trying to shoot down the drone or simply firing warning shots. But one official briefed on the episode said the Iranian planes — identified as Soviet-made SU-25 jets known as Frogfoots — carry cannon for supporting ground troops and are not especially adept at air-to-air combat.
Little said the Predator was flying about 16 nautical miles from Iran while conducting a routine maritime surveillance mission. He stressed that Iran’s territorial limits extend 12 nautical miles from its shores, and that the drone never strayed into Iranian space.
Given the critical role of the Persian Gulf and the Strait of Hormuz in the international shipping of petroleum products, the US military conducts regular seaborne and aerial surveillance of those routes.
The advanced sensor technology aboard the Predator is likely to have allowed it to get a detailed look at Iran even from the distance cited by officials.
Little said that a protest was delivered to Iran via the Swiss Embassy in Tehran and that the Defense Department would not halt surveillance.
He cautioned Iran that the United States had ‘‘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.’’
Late last year, a CIA surveillance drone crashed deep inside Iranian territory while on a mission that was believed to be designed to map suspected nuclear sites.
While some Iranian officials said that drone was shot down or guided to land safely through electronic intervention of its guidance system, US officials said it had crashed after a technical malfunction.
Assessing Iranian intentions has been difficult. US officials said the two Iranian warplanes involved in the episode were under command not of the air force, but of the Revolutionary Guard Corps, whose activities are routinely more brazen than those of the conventional Iranian military.