Donald Trump wants Elon Musk to slash regulations as he reveals ...

US president-elect Donald Trump is expected to continue his hardline White House appointments and name Florida senator Marco Rubio — whom he has previously called "lightweight" — as secretary of state.

Rubio ran against Trump for the 2016 Republican presidential nomination, in a campaign that saw him trade barbs with the billionaire on several occasions.

Trump made fun of Rubio's make-up, saying it appeared he had put it on with a trowel, and accused him of being a "nervous basket case" and sweating too much.

In social media posts, he also referred to Rubio as a "lightweight" and "Mr Meltdown".

Meanwhile, Rubio accused Trump of "having a meltdown" backstage at one of the debates, and questioned whether his rival had requested a full-length mirror "to make sure his pants weren't wet".

At the time, he told CNN Trump was "the most vulgar person to ever aspire to the presidency".

Despite those insults, Rubio has become more closely aligned with Trump in subsequent years, and he is now firmly in the president-elect's fold.

While not yet announced — and Trump has a history of changing his mind — Rubio's looming appointment was being openly discussed in US political circles.

Former Republican congressman Adam Kinzinger, a regular Trump detractor, told CNN Rubio was "somebody that understands foreign policy. And that's going to be important".

Elon Musk reportedly spent about $US200 million helping Trump's campaign. (Reuters: Carlos Barria/File)

As the appointments for Trump's incoming team continue to be announced, he confirmed Elon Musk and former Republican presidential candidate Vivek Ramaswamy would lead the Department of Government Efficiency.

Musk and Ramaswamy "will pave the way for my administration to dismantle government bureaucracy, slash excess regulations, cut wasteful expenditures, and restructure Federal Agencies," Trump said in a statement.

Trump also revealed Fox News host and Army veteran Pete Hegseth would serve as his defence secretary.

"With Pete at the helm, America's enemies are on notice — our military will be great again, and America will never back down," Trump said in a statement.

During his time at Fox, Hegseth, a 44-year-old former infantry captain in the Army National Guard who has served in Afghanistan, Iraq and Guantanamo Bay, Cuba, regularly had Trump on his show.

The president-elect also nominated former Texas Republican congressman John Ratcliffe to run the CIA.

Ratcliffe was director of national intelligence for part of Trump's previous administration, and was criticised for making public unverified information about Russia's influence on the 2016 US presidential election.

Both men will need to be confirmed by the US Senate before officially taking up the new roles.

Former Arkansas governor Mike Huckabee would be the new US ambassador to Israel.

It's anticipated Huckabee, who's consistently defended Israel, will build even closer ties between the state and the US.

Rubio's appointment would come amid a deteriorating global security landscape.

Wars in the Middle East and Ukraine continue to rage, although Trump has insisted he will end both.

That will be easier said than done.

Donald Trump and Marco Rubio campaign in North Carolina earlier this month. (Reuters: Jonathan Drake)

Israel and Iran have exchanged direct fire several times in the past year in a development that has put the region on edge.

Earlier this month, Qatar withdrew as the regional intermediary in ceasefire talks between Israel and Hamas, citing a reluctance from the parties to compromise.

Rubio is an ardent supporter of Israel, and has laid the blame for the war in Gaza on Hamas.

Meanwhile, although Russia and Ukraine do not release their official death tolls, they are estimated to be in the hundreds of thousands on both sides.

If anything, that war is expanding. An emboldened North Korea in October sent troops to join Vladimir Putin's invasion. It also ramped up its own missile testing program, to the dismay of Seoul, a key US ally.

During Trump's previous stint in the White House, Rubio co-sponsored a bill that would make it harder for the US to withdraw from NATO — something the then-president threatened on multiple occasions.

In September, Rubio told NBC he was a supporter of Ukraine, but wanted the war there to end.

The US is Ukraine's largest backer in terms of single nations, providing direct military assistance as well as humanitarian aid.

"I think the Ukrainians have been incredibly brave and strong in standing up to Russia. But at the end of the day, what we are funding here is a stalemate war, and it needs to be brought to a conclusion, or that country is going to be set back 100 years," Rubio said.

Rubio has previously served as a co-chair of a bipartisan congressional committee that drew up strict policy stances on China.

Rubio's appointment would continue a series of hardline West Wing picks, that have already seen Tom Homan will oversee his strict immigration blueprint, a so-called "border Czar".