Media playback is unsupported on your device

Obama pokes fun at Donald Trump

1 May 2011 Last updated at 09:45 BST

President Obama has been mixing comedy with some early campaigning at the White House correspondents' annual dinner.

After weeks of attacks from his would-be Republican challenger Donald Trump, he joked about having to release his birth certificate to prove he was born in America.

Daniel Griffiths reports.