02/12/2016 12:26 PM AEDT | Updated 03/12/2016 9:14 AM AEDT

Donald Trump Taps Retired Gen. James Mattis As Defense Secretary

President-elect Donald Trump has chosen retired Marine Gen. James Mattis to lead the Defense Department, he announced Thursday in Ohio.

The pick was first reported by The Washington Post and CNN, which cited anonymous sources, but Trump spokesman Jason Miller later tweeted that “no decision has been made yet” for the open post.

Trump said Mattis’ appointment would be announced Monday, and told a rally crowd: “Don’t tell anyone.”

“I want to save the suspense for next week. I won’t tell you. I refuse to tell you,” he said.

The 66-year old general, whose nicknames include “Mad Dog” and “Warrior Monk,” was unexpectedly replaced as head of U.S. Central Command in 2013 amid disagreements with the Obama administration over his aggressive posture toward Iran. According to Foreign Policy, Mattis “pushed the civilians so hard on considering the second- and third-order consequences of military action” against the Iranian regime.

Gary Cameron / Reuters

Mattis will face a legal obstacle if he decides to take the job. Federal law prohibits commissioned officers from serving as secretary of defense until seven years after active duty. Congress passed the law in 1950, after Gen. George C. Marshall was appointed to the job. The spirit of the law meant to ensure civilian control over the military ― often seen as a tradition among liberal democracies.

Congress will need to pass legislation exempting Mattis from the statute ― a task that ought to be easy for Republicans, who control both chambers.

Mattis has already shown some ability to influence the president-elect, who often spoke of his affinity for generals like George Patton on the campaign trail. This month, after Trump and Mattis met in New Jersey, Trump said he was “very impressed” with Mattis’ answer on waterboarding.

“’He said, “I’ve never found it to be useful,”’ Trump said during an interview with reporters and editors of The New York Times.

Marina Fang contributed.