"An expedited change in leadership was needed," the official said in Washington on Tuesday of the decision to relieve Aucoin of his command.
The Navy declined to comment on any plans to relieve Aucoin, which was first reported by the Wall Street Journal.
The official told Reuters that Admiral Scott Swift, the commander of the U.S. Pacific Fleet, would relieve Aucoin, a three-star admiral, when the two meet in Japan.
It was not clear when the formal announcement would be made. The Seventh Fleet is headquartered in Japan.
Aucoin was due to step down next month, with Phillip Sawyer, deputy commander of the Pacific Fleet and a submariner by trade, slated to succeed him. Aucoin came up through the Navy's air wing as an F-14 navigator.
The move to replace Aucoin comes days after the collision between a guided-missile destroyer and a merchant vessel east of Singapore and Malaysia before dawn on Monday, the fourth major incident in the U.S. Pacific Fleet this year.
An international search-and-rescue operation involving aircraft, divers and vessels from the United States, Singapore, Malaysia, Indonesia, and Australia is looking for the 10 U.S. sailors missing since the accident.
The U.S. Navy is also working to identify a body found by the Malaysian navy about eight nautical miles northwest of the collision site.
The latest collision has already prompted a fleet-wide investigation and plans for temporary halts in U.S. Navy operations.
The USS John S. McCain's sister ship, the USS Fitzgerald, almost sank off the coast of Japan after colliding with a Philippine container ship on June 17. The bodies of seven U.S. sailors were found in a flooded berthing area after that collision.
The USS John S. McCain and the tanker Alnic MC collided on Monday while the U.S. ship was approaching Singapore on a routine port call. The impact tore a hole in the warship's port side at the waterline, flooding compartments that included a crew sleeping area.
(Reporting by Phil Stewart in WASHINGTON and Tim Kelly in TOKYO; Writing by Sam Holmes; Editing by Paul Tait)
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)