Underwood took the mic after Trump’s inauguration speech, but the music broke off after barely a second of audio, leaving the crowd at the US Capitol Rotunda whispering and muttering in silence.

Trump himself kept a stone-faced look as the silence extended.

“Help me out here,” Underwood said, before launching into the song without audio backing.

Underwood, backed by an armed forces choir, completed the song a cappella and was greeted with applause.

She was announced as the singer at Trump’s inauguration about a week ago.

“I love our country and am honoured to have been asked to sing at the inauguration and to be a small part of this historic event,” Underwood said in a statement to CNN.

“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.”

The Grammy-winning artist is as high-profile as you can get in country music, not only with numerous platinum hits, but also with public-facing, mainstream business associations.

Underwood is the face of Sunday Night Football and is set to make her debut this March as a judge on ABC’s American Idol – the singing competition show that catapulted her to fame when she won in 2005.

Underwood has kept her politics under wraps over the course of her career.

In her statement, she did not mention Trump by name and kept her focus on unifying the country – still, Underwood’s decision to publicly align with Trump is a big statement for any star, particularly one as private as the singer.