New York: Taking everyone by surprise, US President Barack Obama charmed a fundraising event here by crooning American gospel and soul singer Al Green's hit 'Let's stay together' that underlined a theme of his re-election campaign.

After taking the stage for the fundraiser at Apollo Theater in Harlem, Obama showed off his singing skills.

He began by saying, "To know that Al Green was here..." but paused briefly.

He then began to sing the opening line of the hit 1972 song, "I'm sooo in love..."

The crowd of 1,400 supporters went wild, cheering and applauding the President.

The lyrics of full opening stanza of the song read: "I'm, I'm so in love with you. Whatever you want to do is alright with me, cause you make me feel, so brand new.    And I want to spend my life with you".

The tune's refrain underlined a theme of Obama's re-election campaign: "Let's, let's stay together".

"Those guys didn't think I would do it. I told you I was going to do it," Obama said with a smile, glancing off stage.

"The sandman did not come out. Now don’t worry, I cannot sing like you, but I just wanted to show my appreciation," he said.

The appearance at Apollo was hosted by Tony Award-winning composer and actor Lin Manuel Miranda with performances by Green and vocal artist India Arie.

Tickets were priced at USD 200 each for general admission.

Obama reached New York late in the evening for the fund-raising event after a hectic day that took him from Washington to Florida and also saw him unveiling a new tourism policy in Disneyland.

He also attended dinner at the home of the movie-maker Spike Lee.

Obama used the fundraisers to criticise his Republican rivals, saying they wanted tax cuts for the wealthy at the cost of spending on education and research.

"I should pay more taxes and folks in my income bracket should pay more in taxes," Obama said.

"All of us have to do our part. That should not be a Democratic idea or a Republican idea -- that should be an American idea.

"It is about taking responsibility for the country," said Obama on this occasion.

(Agencies)