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Kevin Sweeney, chief of staff of the U.S. Department of Defense, announced Saturday his resignation from the post.

"After two years in the Pentagon, I've decided the time is right to return to the private sector," Sweeney said in a statement.

His departure comes after former Secretary of Defense Jim Mattis stepped down last month.

Mattis, who worked with Sweeney when he led the U.S. Central Command, picked Sweeney to be his chief of staff in early 2017. Sweeney retired as a rear admiral from the U.S. Navy in 2014.

Sweeney's decision is the latest by a senior official to leave the Pentagon. Earlier this week, Pentagon spokeswoman Dana White announced her departure.

Deputy Defense Secretary Patrick Shanahan is now acting U.S. secretary of defense.