The Senate Armed Services Committee overwhelmingly approved retired Marine Sen James Mattis for defence secretary on Wednesday (18 January), in a vote 26-1. President-elect Donald Trump's nomination to run the Pentagon will now head to the full Senate, which has the final say on approving Cabinet appointees.

"I think it is really a testimony to the man because so many members of the committee had known him when he was [commander of US] Central Command and they know of his reputation," said Arizona Senator John McCain, who leads the committee. "You know he's a very unique individual."

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The Senate could hold a final confirmation vote on Friday (20 January) after Trump is sworn into office and the general's nomination becomes official, Stars and Stripes reported.

Mattis, who goes by the nickname "Mad Dog," is largely supported in the Senate. According to Stars and Stripes, Democratic New York Senator Kirsten Gillibrand was the only committee member to vote "no" on Wednesday. He is expected to be easily confirmed, which would make him the first career military officer in almost seven decades who has needed a special waiver to lead the Pentagon.

The retired general received his waiver from Congress last week in a vote 24-3. Gillibrand and fellow Democrats Richard Blumenthal and Elizabeth Warren all voted against the waiver. The last person to be granted the waiver was George Marshall in 1950.

According to Stars and Stripes, Mattis' confirmation hearing last week went relatively smooth, though it did reveal some policy differences with Trump, particularly on the Nato alliance and Russia. Trump has been very vocal about his criticisms of the alliance while also suggesting a thawing of relations with Russia.

Mattis, who helped lead the Nato alliance, told the committee he would strongly support the US treaty commitments and labeled Russia as a key threat to the alliance. "Nato from my perspective, and I served once as the Nato alliance supreme allied commander, is the most successful military alliance in modern world history, maybe ever," he testified.