President-elect Donald Trump has reportedly tapped retired Marine Gen. James Mattis for defense secretary.

The Washington Post reported the most recent Cabinet pick late Thursday afternoon, citing people familiar with the decision. A formal announcement is likely to come early next week.

The appointment would require Congress to pass a waiver on a law that prevents a secretary of defense from having served in active duty within the last seven years. Mattis retired as chief of U.S. Central Command in 2013 after being in the military for more than 40 years.

Congress has granted the waiver only once before. That was in 1950 when Gen. George Marshall was appointed to lead the Pentagon under President Harry Truman.

Mattis, whose affectionate nicknames include “Mad Dog” and “Warrior Monk," is popular among both Republicans and Democrats in Washington, D.C., as well as highly respected in U.S. military circles.