LOS ANGELES • 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 talk-show host Ellen DeGeneres in an interview aired 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 United States sales records and quickly became last year's best-selling album with worldwide sales of about 15 million.

The November release made it ineligible for Grammy consideration on Monday.

Accompanied by just a piano on the Grammys 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.

She 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.

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

REUTERS