Backed by a cruiser, destroyer and with almost 80 planes and helicopters on board, the USS Carl Vinson carrier strike group "arrived in the US 5th Fleet area of responsibility (AOR)" on January 9," a Fifth Fleet statement said.
That area covers the Gulf, the Red Sea, the Gulf of Oman and parts of the Indian Ocean.
Pentagon Spokesman John Kirby told reporters that the Carl Vinson was "not in the Gulf" and had not gone through the Strait of Hormuz - a key oil route which Iran has threatened to close as tensions with the West flare.
The Carl Vinson was due to relieve another aircraft carrier, the USS John Stennis, which is in the region, Kirby said.
"Her deployment in that area is routine, long-planned. There's nothing unusual about that," Kirby explained.
"The numbers of carrier strike groups attached to the Centcom AOR change all the time and it's been consistently that way," he said.
"The fact that there are two carriers in that AOR is not an indication of anything specific in respect to Iran," the Spokesman stressed, insisting that "there is no change to force posture in the region."
Despite the Pentagon's denials of a build-up in the region, the USS Abraham Lincoln was in the Indian Ocean and en route to join the Carl Vinson, according to the US Navy.