Washington DC - US Defense Secretary Pete Hegseth said Monday the military will keep assisting President Donald Trump's "mass" migrant deportations, as he arrived for his first formal day of work at the Pentagon.

Hegseth – confirmed by Republicans despite concerns over his inexperience, and alleged record of heavy drinking and domestic violence – is one of Trump's most contested cabinet picks.

After barely squeaking through his confirmation vote, the former Fox News host made clear that he would work to carry out the president's hard-right agenda, including using the military in deportations.

"Support of mass deportations in support of the president's objective – that is something the Defense Department absolutely will continue to do," Hegseth told reporters on the steps of the Pentagon.

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Colombia turned back two US military aircraft with its citizens aboard over the weekend, prompting Trump to threaten economic tariffs that ultimately pushed the US ally to back down and agree to accept the repatriation flights.

Hegseth also said more executive orders are coming on removing diversity, equity, and inclusion programs from the Pentagon and reinstating troops who were pushed out because they failed to comply with the since-rescinded Covid-19 vaccine mandate.

"Our job is lethality and readiness and war fighting and [to] hold people accountable," he said. "The lawful orders of the president of United States will be executed inside this Defense Department – swiftly and without excuse."

On Friday, three Republican senators voted against confirming Hegseth, resulting in a 50-50 tie that required Vice President JD Vance to cast the deciding ballot – only the second time in history a tie-breaker has been needed to save a cabinet nominee.

In confirming Hegseth, Republicans brushed aside his lack of experience leading an organization anywhere near the size of the Defense Department – the country's largest employer with some three million personnel.