"Matt is a strong warrior and loyal Patriot, who will ensure the United States' interests are advanced and defended," Trump said in a statement.

"Matt will strengthen relationships with our NATO Allies, and stand firm in the face of threats to Peace and Stability - He will put AMERICA FIRST," Trump said.

Whitaker served as acting attorney general during Trump's first term.

NATO has been bracing for Trump's return to the White House after he threatened in February to stop guaranteeing US protection for member states if he did not believe they contributed enough financially.

Alliance chief Mark Rutte was quick to congratulate the Republican after his election victory and played up the positive impact he said Trump could have.

"His leadership will again be key to keeping our Alliance strong. I look forward to working with him again to advance peace through strength through NATO," Rutte said.