Lady Gaga and Tony Bennett duet at inaugural ball

Lady Gaga teamed up with Tony Bennett at a private ball for Barack Obama's staff on Tuesday (22Jan13) to thank them for their hard work during the President's re-election campaign.

The Poker Face singer invited the veteran crooner to join her onstage as she headlined the event for aides who helped Obama win four more years in the White House.

The pair performed The Lady Is A Tramp, which they covered for Bennett's album Duets II, after the President honoured supporters for their hard work, telling guests they represented his "deepest hopes for America".

He said, "It makes me know that America's future is in good hands. As long as all of you understand the immense and incredible power that you possess when you work together, when you join voices."

According to the Associated Press, proceeds from the event will be donated to a memorial fund for Alex Okrent, a 29-year-old campaign worker who collapsed and died at Obama's headquarters in Chicago, Illinois in July (12).

Obama paid tribute to Okrent, adding, "Alex was one of you. This incredibly thoughtful, talented, compassionate, caring young person who decided to get involved because he thought he could make a difference. And tragically, he ended up leaving us while working on the campaign... It was heartbreaking. It reminded us of how precious our time on this earth is."

Jay-Z and Arcade Fire headlined a similar party for staff in 2009 after Obama's first inauguration.