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.