According to CBS News, Underwood was supposed to perform at the beginning of the ceremony, but the programme was delayed, and Trump and J.D. Vance needed to be sworn in.
Eventually, Underwood mouthed the words “I can just sing it”, and told the audience, “You know the words, help me out here”, before she started singing a capella.
“I am humbled to answer the call at a time when we must all come together in the spirit of unity and looking to the future.”
Earlier in the ceremony, Lee Greenwood performed God Bless the USA before Trump took his oath of office and classical singer Christopher Macchio sang the national anthem and O America.
Greenwood also performed at Trump’s 2017 inauguration, as well as those of former presidents Ronald Reagan in 1985, George H.W. Bush in 1989, and George W. Bush in 2001.
More celebrity performances will take place at three different inaugural balls during the evening of Monday, January 20 local time.
Rascal Flatts and Parker McCollum will perform at the Commander in Chief Inaugural Ball, according to CBS, while Jason Aldean, The Village People and Nelly are scheduled to perform at the Liberty Inaugural Ball.
Gavin DeGraw will sing at the Starlight Ball. Trump is expected to speak at all three events.
You can follow the Herald’s live coverage of President Trump’s inauguration day here.