CINCINNATI (Reuters) – U.S. President-elect Donald Trump said on Thursday night he would nominate retired Marine Corps General James Mattis, known as “Mad Dog” and renowned for his tough talk and battlefield experience in Iraq and Afghanistan, to lead the Pentagon.

“We are going to appoint Mad Dog Mattis as our secretary of defense,” Trump told a rally in Cincinnati. He said the formal announcement would be made on Monday.

The choice of a seasoned military strategist would be another indication that Trump, a Republican, intends to steer U.S. foreign policy away from Democratic President Barack Obama’s increased reliance on U.S. allies to fight Islamist militants and to help deter Russian and Chinese aggression in Europe and Asia.

Mattis is a revered figure in the Marine Corps and known for his distrust of Iran.

The Washington Post and CNN reported earlier that Trump had chosen Mattis, but Trump spokesman Jason Miller said earlier on Twitter that “no decision has been made yet with regard to Secretary of Defense.”

While the nomination of the 66-year-old Mattis would likely be popular among U.S. forces, it would have to clear a bureaucratic hurdle.

Because he retired only in 2013, Mattis would need the U.S. Congress to waive a requirement that a defense secretary be a civilian for at least seven years before taking the top job at the Pentagon. His impressive combat record, however, may deter some Senate Democrats from trying to block his nomination.

Trump has described Mattis as “a true general’s general.”

The New York real estate magnate famously asserted last year: “I know more about ISIS than the generals do.”

(Reporting by Emily Stephenson in Cincinnati and Doina Chiacu and Eric Beech in Washington; Editing by Sandra Maler and Peter Cooney)