During the first stop of his "USA Thank You" tour Thursday night, President-elect Donald Trump confirmed that he has chosen Jim Mattis to serve as his secretary of defense, apparently hoping the retired Marine general's career as a combat commander will help him overcome a legal ban on former military officials serving in that role within seven years of retirement.

“I want to save the suspense for next week. I don’t wanna let it out of this room,” he teased the crowd at the U.S. Bank Arena in Cincinnati. “So I will not tell you that … we are going to appoint 'Mad Dog' Mattis as our secretary of defense. But we’re not announcing it until Monday, so don’t tell anyone."

The decision was first reported by The Washington Post, citing unnamed officials advising the campaign, and confirmed to sources who spoke with U.S. News. Trump is expected to announce his picks for both Defense and State next week.

Mattis would be the second retired general serving in Trump's Cabinet and one of around five being considered for key positions following his decision to pick as his national security adviser former Defense Intelligence Agency chief Michael Flynn, a former three-star general fired from that job in 2014. Trump also has met with former Central Command chief David Petraeus, who also headed the CIA, for a possible pick as secretary of state.

Trump transition team communications director Jason Miller tweeted shortly after the news broke that the Mattis nomination was not yet final.

"No decision has been made yet with regard to secretary of defense," he wrote.

A source advising the transition team confirms to U.S. News that Trump wants Mattis as his defense secretary but says the team has realized the perception problem of having too many former generals serving in top Cabinet positions designed to ensure civilians ultimately make key foreign policy and national security decisions.

"It begins to look like Chile in the 1970s if it's three-stars as [national security adviser], a retired four-star as 'SecDef,' and a retired four-star at State," the source says. "Although individually they may be extremely meritorious, all together it looks different."

If Trump locked in his decision on Mattis, that would disqualify Petraeus in the president-elect's mind, the source says, explaining the disparity between The Post report and Miller's tweet since Trump has not yet finalized his choice for secretary of state. Trump is also believed to be considering Mitt Romney, the former governor of Massachusetts and 2012 GOP presidential candidate, and Sen. Bob Corker, R-Tenn., to lead State.

Mattis served in the Marine Corps for 44 years, including combat tours in the first Gulf War, in Afghanistan where he led some of the first troops to infiltrate the country in 2001, and in Iraq, where his 1st Marine Division helped spearhead the 2003 invasion. He earned a reputation as a "Marine's Marine" with nicknames like "Mad Dog," "Chaos" – his radio call sign – and "the warrior monk" for the extensive library he traveled with and the fact he never married.

The law currently forbids members of the military from serving as secretary of defense within seven years of retiring from the armed forces. Congress would have to pass legislation to allow Mattis to take up the assignment.

Sen. John McCain, chairman of the powerful Armed Services Committee, issued a glowing statement about Mattis' accomplishments shortly after the retired general met with Trump in November.

"He is a forthright strategic thinker," the Arizona Republican said. "His integrity is unshakable and unquestionable. And he has earned his knowledge and experience the old-fashioned way: in the crucible of our nation's defense and the service of heroes."