Trump is attending a luncheon at Congress, but before beginning his meal, he took his first actions as president.

He signed into a law a waiver to allow Defense Secretary-designate James Mattis, a retired US Marine Corps general, to serve, Trump's spokesman said. 

Mattis requires a Senate waiver, since former service members are required to be out of uniform for over seven years to become Defence Secretary.

He also formally sent his cabinet nominations to the Senate, and called for a national day of patriotism.