US vice president Joe Biden dropped off to sleep while his boss was delivering a much-hyped speech on saving the nation's economy.

As President Barack Obama worked his way through statistics and policy goals during a 30-minute speech, his right-hand man couldn't resist the urge to nod off.

Mr Biden's nap managed to steal some of the limelight from Mr Obama's speech, and it was not the first time that the vice president had blundered during a major political event.