British superstar Adele said she cried all day after what was supposed to be a triumphant return to the Grammys stage turned into a shaky live performance in which she sang off-key.

"I was so embarrassed," the "Someone Like You" singer told US talk show host Ellen DeGeneres in an interview recorded on Wednesday and to be broadcast on Thursday.

"I cried pretty much all day yesterday," said Adele, a six-time Grammy winner in 2012. "I don't feel like it could go that much worse than the Grammys, though."

Monday's Grammy Awards marked the biggest appearance for the 27-year-old singer in four years. It followed the release in November of "25," which broke US sales records and quickly became the best-selling album of 2015 with worldwide sales of some 15 million. The November release made it ineligible for Grammy consideration on Monday.

Accompanied by just a piano on the Grammy stage in Los Angeles, she sang her new single "All I Ask." But the performance was marred by technical issues when a microphone fell onto the piano's strings, and she turned in an uncharacteristically shaky performance, hitting sharp and flat notes.

Adele told DeGeneres she heard immediately that the song was not going well and wished she had stopped and started again.

"Next time I have any sound issues, I am gonna stop. I'll be like, sorry that's not working for me. If we have time to do it again, let's do it; otherwise, bye!," she said.

She also acknowledged feeling more pressure now to perform well than a few years ago. "The more successful I get, the more pressure there is, really," she said.

Adele starts a nine-month-long, sold-out European and North American tour on Feb. 29.