Iranian patrol boats and aircraft shadowed a U.S. aircraft carrier strike group as it transited the Strait of Hormuz on Tuesday.
The passage ended a Gulf mission that displayed Western naval power amid heightened tensions with Tehran, which has threatened to choke off vital oil shipping lanes.
But officers onboard the USS Abraham Lincoln said there were no incidents with Iranian forces and described the surveillance as routine measures by Tehran near the strategic strait, which is jointly controlled by Iran and Oman.
Although U.S. warships have passed through the strait for decades, the trip comes during an escalating showdown between Iran and the West over the Islamic Republic's nuclear program. The last time an American carrier left the Gulf _ the USS John C. Stennis in late December _ Iran's army chief warned the U.S. it should never return.
The Lincoln was the centerpiece of a flotilla that entered the Gulf last month along with British and French warships in a display of Western unity against Iranian threats. There was no immediate comment by Iran about the Lincoln's departure.
Iran's Revolutionary Guard has said it plans its own naval exercises near the strait, the route for a fifth of the world's oil supply. But Iran's military has made no attempts to disrupt oil tanker traffic _ which the U.S. and allies have said would bring a swift response.
Two American warships, one in front and one in the rear, escorted the Abraham Lincoln on its midday journey through the strait and into the Arabian Sea after nearly three weeks in the Gulf, which is frequently visited by U.S. warships and includes the headquarters of the U.S. 5th Fleet in Bahrain. The strait is only about 30 miles (50 kilometers) across at its narrowest point.
On one side, the barren, fjord-like mountains of Oman were visible through the haze. Iran's coast was just beyond the horizon on the other side of the ship, but too far away to be seen.
Gunners in red jerseys manned the 50-caliber machine guns as the ships moved out of the Gulf. An Iranian patrol boat pulled nearby.
Later, just after the Lincoln rounded the "knuckle" _ the nub of Oman jutting out at the southern end of the strait _ an Iranian patrol plane buzzed overhead. Another patrol boat was waiting further down the coast, said Rear Adm. Troy Shoemaker, commander of the Abraham Lincoln Carrier Strike Force.
Besides Iran's regular patrol boats, the Revolutionary Guard operates a large number of small, fast-attack boats. Some are armed with only a machine gun, while others also carry anti-ship missiles. They can be difficult to spot because they resemble the swift-moving smuggling boats that ply the strait.
Shoemaker said none of those fast boats appeared Tuesday, likely deterred by the rough seas.
He predicted before the transit that the Iranians would likely keep a close eye on the Lincoln throughout its passage, including with ground-based radars. He wasn't surprised by the attention from Iranian forces.
"We would do the same things off the coast of the United States ... It's more than reasonable. We're operating in their backyard," he said. "We've been doing it for years."
Several U.S. choppers flanked the carrier group throughout the transit, watching out for potentially hostile vessels and relaying real-time pictures back to the Lincoln's crew.
Dozens of F/A-18 strike fighters and other planes in Lincoln's embarked air wing sat parked silently on deck throughout the trip. Today was a no-fly day for their crews, though some fighters were prepped and armed, ready to launch in as little as 15 minutes should things go wrong.
Officers on board were eager to describe the transit, in which the Lincoln was accompanied by the cruiser USS Cape St. George and destroyer USS Sterett, as a routine maneuver despite the growing speculation that Israel could launch a military strike against Iran's nuclear program.
The U.S. and allies fear Iran's uranium enrichment program could eventually lead to the production of weapons-grade nuclear material. Iran claims it only seeks reactors for energy and medical research.
"I wouldn't characterize ... us going through the strait as: 'Hey, this is a huge show of force, we're coming through.' It's an international strait to transit. We're going from one body of water to the other," said Capt. John Alexander, the Lincoln's commanding officer, as preparations for the trip got under way late Monday.
The Lincoln is expected to provide air support for the NATO mission in Afghanistan starting Thursday. Navy brass in the Gulf say another American carrier is due back through the strait soon, but gave no firm timetables.