American President Barack Obama was met with a birthday serenade from actress Jennifer Hudson on Wednesday.

The 29-year-old Oscar winner channelled Marilyn Monroe’s 1962 Happy Birthday performance to President John F Kennedy, as she sang at a special Democratic Party fundraiser in Chicago.

Obama, who turned 50 yesterday grinned when the performance began, then kissed Hudson on the cheek and clasped her hand as he said thank you.

Jazz musician Herbie Hancock and rock band OK GO also performed at the Aragon Ballroom, which costs $40,000 to rent.

Tickets to the fundraising dinner cost a hefty $35,800 per person.

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Michelle was not present on Wednesday night, but yesterday the family hosted an intimate birthday barbecue for the President in the White House Rose Garden.

This comes as a welcome distraction from the near debt-default disaster, which was averted with a Congress deal on Monday.

Obama said in an online talk to supporters: “I know that over the last two-and-a-half years there have been times when people have been frustrated.

"This past week was a frustrating week."

Michelle sent an email to Democratic voters asking them to sign an electronic card for her husband. She said in the email that things will continue to be a challenge with the re-election campaign around the corner.

She said: "Every day, I see Barack make choices he knows will affect every American family. That's no small task for anyone – and proof that he's earning every last one of those grey hairs."