Brown would become the second Black officer to serve as chairman of the Joint Chiefs of Staff -- after Colin Powell from 1989-1993 -- at a time when the Pentagon is headed by Lloyd Austin, the country's first Black secretary of defense.

The nomination for Brown to replace Milley -- whose term ends in September -- will be made at a Rose Garden ceremony, the White House said in a statement.

Brown, who currently serves as chief of staff of the US Air Force and was commissioned as an officer in 1984, is an experienced pilot with more than 3,000 flight hours, 130 of them in combat.

He has commanded a fighter squadron and two fighter wings, as well as US air forces under the Central Command and Indo-Pacific Command.

Following the 2020 murder of Black man George Floyd by a white police officer in Minnesota, Brown recorded an emotional video about his personal experiences, including with discrimination in the American military.

"I'm thinking about my Air Force career, where I was often the only African American in my squadron or as a senior officer, the only African American in the room," Brown said.

"I'm thinking about the pressure I felt to perform error-free, especially for supervisors I perceive had expected less from me as an African American," he said.

- 'Working twice as hard' -

"I'm thinking about having to represent by working twice as hard to prove their expectations and perceptions of African Americans were invalid."

Brown -- who is known by the initials "CQ" -- will still need to be confirmed by the US Senate in order to replace Milley, who has served as chairman since 2019.

But a swift confirmation is far from guaranteed, as Republican Senator Tommy Tuberville has stalled some 200 senior military nominations over his opposition to Pentagon policy on reproductive health care.

Milley has helped Austin helm US-led international efforts to support Ukraine's fight against invading Russian forces -- backing that has been a key part of battlefield successes by Kyiv's forces.

His time in the post was also marked by the chaotic US withdrawal from Afghanistan that was capped by the Taliban's takeover of the country. He subsequently described the war as a "strategic failure."

During Donald Trump's presidency, the general reportedly contacted China amid concerns that the billionaire-turned-politician could seek to spark a conflict with Beijing or Tehran, sparking accusations that he was seeking to circumvent civilian control of the military.

In another controversial situation, Trump had then-defense secretary Mark Esper and Milley walk alongside him in front of the White House after police cleared the street of people protesting Floyd's murder.

Both later expressed regrets they took part in what was widely labelled a political "photo op" for the president.

Milley, who like Austin has repeatedly come under fire from conservatives over the US military allegedly becoming too "woke," has warned against the politicization of the country's armed forces.

"You never want the military in actual politics -- very dangerous," Milley told lawmakers in late March. "We need to keep the military out of politics, we need to keep it apolitical and non-partisan at all times."