SINGAPORE - Surprise guest Taylor Swift debuted her single New Year's Day on Jimmy Fallon's Tonight Show, in what proved to be an emotional tribute to his recently deceased mother.

Fallon, 43, returned to late night talkshow The Tonight Show on Monday (Nov 13) after taking a week off to mourn the loss of his mother Gloria who died at the age of 68.

During a monologue at the start of the show, he said: "When we were little, my mum would walk us to the store-me and my sister-and we would hold hands. And she would squeeze my hand three times and say, 'I love you,' and I would squeeze back, 'I love you, too.' Last week I was in the hospital, at her side. I grabbed her hand and I squeezed, 'I love you,' and I just knew we were in trouble."

Swift's unscheduled appearance saw her performing a moving rendition of New Year's Day off her new album Reputation.

Her song was all the more poignant as the lyrics in the second verse say: "You squeeze my hand three times in the back of the taxi/ I can tell that it's gonna be a long road/I'll be there if you're the toast of the town, babe/Or if you strike out and you're crawling home."

The 27-year-old Grammy winner and Fallon shared an emotional hug at the end of her performance.

The Tonight Show producer Mike Dicenzo took to Twitter to say that Swift said yes to appearing on the show with "zero hesitation".

Reputation was released last Friday and has sold more than one million copies in the first four days of its release in the United States, making it the best-selling album of 2017 so far.