ABOARD THE USS ABRAHAM LINCOLN: Iranian patrol boats and aircraft shadowed a US aircraft carrier strike group as it passed through the Strait of Hormuz on Tuesday, ending a Gulf mission amid heightened tensions with Tehran that include threats 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 US 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 programme. The last time an American carrier left the Gulf — the USS John C. Stennis in late December — Iran’s army chief warned the US it should never return.

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 US 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. The narrow waterway 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.—AP