Donald Trump has picked former Marine Corps Gen. John Kelly to run the Department of Homeland Security, the third retired military officer nominated for a role in the president-elect's Cabinet.

CBS News was first to report on Wednesday that Kelly had accepted the offer. Trump's transition team did not immediately confirm the report. Kelly, who is traveling abroad, did not respond to a request seeking comment.

A formal announcement is expected within days, according to CBS News.

Kelly, the former head of U.S. Southern Command, is well-regarded among Republicans on Capitol Hill and during his service sparred with President Barack Obama's administration on a variety of security and military issues, including the attempt to shutter detention facilities at Naval Base Guantanamo Bay in Cuba. He also holds strong views on border security.

As head of Southern Command, Kelly oversaw not only the controversial prison but also military missions related to security along America’s southern border, drug and weapons trafficking from South America and Central America, and gang activity in the region.

He also boasts extensive experience in the Middle East, having spent about two years leading combat forces against the Islamic State’s Sunni Arab forerunners in Iraq’s Anbar province.

Trump picks director of Homeland Security

President-elect Trump has made his pick for the top U.S. security position. Retired Gen. John Kelly to lead the Department of Homeland Security. Kelly served over 40 years in the Marine Corps. As head of the U.S. Southern Command he gained experience managing security threats posed by criminal networks close to home. "Unless confronted by an immediate, visible or uncomfortable crisis, our nation's tendency is to take the security of the Western Hemisphere for granted. I believe this is a mistake."

He's a Boston native and close friend of Joint Chiefs Chairman Marine Corps Gen. Joseph Dunford. And the 66-year-old veteran has the somber distinction of being the highest-ranking American military official to lose a child in combat during the recent wars. His son, Marine Lt. Robert Michael Kelly, was killed in Afghanistan in 2010. 

Along with the Homeland Security post, Trump reportedly had been considering Kelly for Secretary of State, the most prominent incoming Cabinet post still without a nominee.

News of Kelly’s selection comes just a day after Trump’s formal introduction of retired Marine Corps Gen. James Mattis as the next Secretary of Defense. Last month, Trump tapped former Army Lt. Gen. Michael Flynn to be his National Security Adviser.

Transition officials said Trump is considering several other retired military flag officers for key posts in the new administration, including a meeting with former U.S. European Command leader Adm. James Stavridis on Thursday.

Mattis will need a waiver to serve as Defense Secretary, because of federal laws requiring seven years of separation from the military before appointment to that post.

But no such rules are in place for the Homeland Security head, making Kelly’s confirmation an easier process. He retired from the Marine Corps earlier this year after 45 years of service.

As news emerged that Kelly had accepted Trump's offer, two hawkish members of the Senate Armed Services Committee said they have no reservations with yet another general in Trump's Cabinet.

Asked why Trump is selecting so many generals to fill top posts in his administration, Sen. John McCain said "because they're the most qualified."

Fellow Republican Sen. Lindsey Graham said he would weigh each nominee as an individual.

"We live in very unusual times and the next president will need experienced hands in terms of how you defend the homeland, and having a general officer where that was part of his job is helpful," Graham said.

With reporting by Defense News' congressional reporter Joe Gould.

Leo Shane III covers Congress, Veterans Affairs and the White House for Military Times. He can be reached at lshane@militarytimes.com.