ADVERTISEMENT

Retired Gen. James Mattis, who left the Marine Corps in 2013, needs a waiver to be eligible to be Defense secretary because of a 1947 law barring anyone who was on active duty in the previous seven years from taking the job. The law is meant to ensure that the Defense Department has civilian control.

McCain's blessing is an important step in shepherding Mattis through the confirmation process.

"Senate Armed Services Committee Chairman John McCain is committed to marking up legislation to grant Gen. Mattis a waiver as soon as possible, calling him, ‘Without a doubt one of the finest military officers of his generation and an extraordinary leader,' " Trump spokesman Jason Miller told reporters Friday, reading off a piece of McCain's statement congratulating Mattis.

McCain signaled in a statement Thursday that he would support the appointment, noting that he is "pleased" with the pick and "look[s] forward to moving forward with the confirmation process as soon as possible in the new Congress."

After multiple reports emerged Thursday that Trump picked Mattis, Miller denied via Twitter that a decision had been reached. But hours later, Trump confirmed his choice at a rally in Cincinnati.

"We are going to appoint ‘Mad Dog’ Mattis as our secretary of Defense,” Trump told the crowd. “But we’re not announcing until Monday, so don’t tell anybody.”