Iran's Revolutionary Guard intercepted a U.S. drone in the Persian Gulf on Tuesday and tried to tow it away, but released it when a U.S. warship approached along with a helicopter, U.S. officials said.
This incident represents the first time Iran has targeted drone units of the US 5th Fleet stationed in the Middle East.
Although the situation was resolved without incident, tensions remain high between Washington and Tehran as world powers continue negotiations with Iran over a deal on its nuclear program.
The Iranian Coast Guard ship Shahid Baziar attached a cable to the Saildrone Explorer drone in the central Persian Gulf in international waters late Monday, said Commander Timothy Hawkins, a spokesman for the US 5th Fleet. The ship then began towing the drone, which contains cameras, radars and sensors for remote monitoring of the seas, Mr. Hawkins said.
The USS Thunderbolt, a US Navy patrol ship, as well as an MH-60 Seahawk helicopter, began following the Iranian guard ship. They radioed the Iranian ship that the drone it was towing was American, Mr. Hawkins said.
"Our response was one that made it clear that it was the property of the US government and that it was operating in international waters and that we intended to take whatever action might be necessary," he told the Associated Press news agency.
Mr Hawkins said the incident ended peacefully after almost four hours. The Iranians detached the cable from the drone and fled the area, while US forces stood nearby.
US General Michael Kurilla, who heads Central Command, praised the crew of the USS Thunderbolt for their response.
"This incident once again demonstrates Iran's destabilizing, illegal and unprofessional activity in the Middle East," he said in a statement.
The Iranian Guard is a paramilitary force that reports directly to Supreme Leader Ayatollah Ali Khamenei. She did not confirm the incident. Iran's mission to the United Nations did not immediately respond to a request for comment.
The US 5th Fleet last year inaugurated its Unit 59, which contains unmanned vehicles. Among the areas under the responsibility of the 5th Fleet is the Strait of Hormuz, in the Persian Gulf, from where 20% of all the world's fuel is transported.
The activity of this fleet extends to the Red Sea and the Suez Canal in Egypt that connects the Middle East with the Mediterranean, as well as the Bab el-Mandeb Strait near Yemen.
The region has experienced a series of sea attacks in recent years. Off Yemen, unmanned boats laden with explosives and floating mines of the Houthi rebels have damaged ships throughout the years of the protracted conflict. Near the United Arab Emirates and the Strait of Hormuz, oil container ships have been seized by Iranian forces. Other ships have been attacked for which the US Navy blames Iran.
These attacks began about a year after then-US President Donald Trump made the decision to withdraw from the Iran nuclear deal, which provided for the lifting of sanctions on Tehran in exchange for drastic limits on uranium enrichment.
Iran already enriches uranium at a rate closer than ever before to the level needed to make it weapons-grade, and officials say openly that Iran could build a nuclear bomb if it wanted to. Iran says its program is peaceful, although Western countries and international inspectors say Tehran has been building a military nuclear program since 2003.