Pete Hegseth, a Fox News co-host, author and US military veteran, has been nominated to lead the world's most powerful military as secretary of defense.

The 44-year-old served as an infantry officer in the National Guard, deploying to Iraq and Afghanistan, and was awarded two Bronze Star medals, his official website says.

He joined Fox News as a contributor in 2014 and now co-hosts Fox and Friends Weekend as well as serves as a host for Fox Nation. He has also authored multiple books.

Hegseth was reportedly considered for secretary of veterans affairs during president Donald Trump's first administration, but was ultimately not selected for the position.

Now, however, he is slated to lead the Pentagon.

Trump hailed Hegseth as "tough, smart and a true believer in America First" in a social media post announcing the nomination. "With Pete at the helm, America's enemies are on notice - Our Military will be Great Again, and America will Never Back Down."

The president-elect also highlighted Hegseth's success as an author, saying his book "The War on Warriors" was a best-seller, and that it "reveals the leftwing betrayal of our Warriors, and how we must return our Military to meritocracy, lethality, accountability, and excellence."

According to the Washington Post, Hegseth's lobbying of Trump in 2019 resulted in the pardon of two service members who were accused of murder, and the reinstatement of rank of a third who was found guilty of posing with a body in Iraq.

Hegseth is an Ivy Leaguer, graduating from both Princeton and Harvard, though his website says he sent his degree back to the latter institution, and he has criticized it on-air for its allegedly leftist leanings.

He lives with his wife and seven children in the southern US state of Tennessee.