President-elect Donald Trump is expected to name Rep Michael Waltz, a Florida Republican, to serve as national security adviser, two sources familiar with the matter told CBS News, the BBC's US partner.

A veteran of the war in Afghanistan and a long-time Trump supporter, Waltz was re-elected to Congress last week - though he will have to vacate his office to serve in the White House.

In this role, Waltz would serve as a key White House adviser on national security and foreign policy matters. It is a prominent role that does not require confirmation.

Senator Marco Rubio of Florida is in talks to be Trump's nominee for secretary of state, though the pick is not a done deal, two sources told CBS.

Waltz and Rubio's offices did not respond to the BBC's request for comment.

A decorated Green Beret and Army veteran, Waltz served multiple tours in Afghanistan, the Middle East and Africa.

He drew on his experiences serving in the Pentagon during the George W Bush administration and in combat in his book Warrior Diplomat: A Green Beret's Battles from Washington to Afghanistan.

Waltz's military experience led to key national security committee assignments when he was elected to Congress in 2018, serving on the Armed Services, Foreign Affairs and Intelligence Committees.

The Florida congressman's expressed views in Congress have hewed closely to Republicans' political views on national security and foreign policy since Trump's election in 2016 - but they also acknowledge the US's key role in global affairs.

Waltz has suggested NATO allies increase their defence spending, though he has not gone as far as Trump and said the US should leave the alliance altogether.

"Look we can be allies and friends and have tough conversations," Waltz said last month.

He has said the US should maintain its support for Ukraine, but in recent weeks he's advocated for a reassessment of the US funds sent to aid the country.

Waltz has also taken a tough line on China while in Congress, and - as chair of the Armed Services Subcommittee on Readiness - argued that the US needs to do more to prepare for conflict in the Pacific.

Since the US's 2021 withdrawal from Afghanistan, Waltz has frequently criticised President Joe Biden and the White House for its decision to leave the country.

Waltz would be the second member of Congress to be tapped to serve in the next Trump administration, which will require him to resign his office in the House of Representatives and potentially slim Republicans' controlling majority.

He would be the fifth national security adviser to serve under Trump, who appointed four different men to serve in the position during his first term. He fired three of them.

Michael Flynn, a retired general and Trump loyalist lasted for only 24 days before he was fired.

Trump then appointed and later dismissed HR McMaster, another retired general who would later criticise the president-elect and his allies in a memoir that he published earlier this year.

John Bolton, who served in the post for 17 months and was Trump's longest-serving national security adviser before also being fired, became highly critical of his former boss and has advocated against the president-elect's efforts to return to the White House.

Robert O'Brien, a lawyer who served in the Bush administration, finished out Trump's first term as national security adviser.

It is not yet certain that Rubio will be nominated to serve as secretary of state, but the Florida Republican's career has set him up to be America's next top diplomat.

Several US media outlets have reported that Rubio is in talks with the Trump transition team over the senior position, but it has not been finalised. It appears the president-elect could still change his mind.

Rubio has built out his resume in the Senate, however.

He serves as the vice-chairman of the Senate Intelligence Committee and sits on the Foreign Relations Committee.

Rubio is considered a foreign policy hawk, particularly toward China and Iran. While supportive of Ukraine, he previously said the ongoing conflict between Russia and Ukraine needs to "be brought to a conclusion”.

Trump and Rubio now have a cordial relationship, but it hasn't always been that way.

Both men ran for president in 2016, and the two developed a bitter rivalry. They clashed on a variety of issues - particularly immigration - and the conflict led to various insults: Trump referred to the senator as “Little Marco” and Rubio mocked Trump's "small hands".

The Florida senator, 53, went on to back his rival and the two patched up their relationship during Trump's first term.

Rubio was an early supporter of Trump in this election’s primary.

The son of working-class Cuban immigrants, Rubio was first elected to the Senate in 2010.

He has since become a stalwart of Republican politics, and was once floated as a potential running mate to 2012 Republican nominee Mitt Romney and to Trump in 2024.