Carrie Underwood dropped by Times Square in New York City Monday evening (Dec. 1) to take part in U2's World AIDS Day concert -- a surprise appearance revealed just hours before the event.

Dressed in a black coat, the country singer treated the audience that gathered on the rainy night to beautiful renditions of 'Change' and 'Something in the Water.' U2's the Edge accompanied Underwood on the former tune.

"I am so honored to be a part of this," Underwood said in between songs. "None of this would be possible without all your support, so thank you, Times Square; thank you, New York; and thank you, America, for all that you do in this fight."

Kanye West also performed during the event, while Bruce Springsteen and Coldplay frontman Chris Martin filled in for U2's lead singer, Bono, who was sidelined due to a bike accident.

“The world reached a tipping point in the fight against AIDS,” Bono says in a press release. “A lot of people are calling it the beginning of the end of AIDS ... Americans don’t know the role they've played in this fight. Tonight’s event is to inform them and thank them."

In September, Underwood performed at the Global Citizen Festival in Central Park. That event, part of the Global Poverty Project, works to eradicate extreme poverty by 2030 and promotes volunteerism.

You Think You Know Carrie Underwood?