Barack Obama vowed that the United States was "ready to lead once more" as he gave his inaugural address after being sworn in as the 44th President of the United States.

As many as a million people, bundled up against the cold, turned out to watch as Mr Obama swore to "preserve, protect and defend" the US constitution as he become the first black man to hold America's highest elected office.

Addressing listeners around the world, the new president said: "As for our common defence, we reject as false the choice between our safety and our ideals.

The inauguration took place amid unprecedented security. About 8,000 police were deployed and a total of 32,000 military personnel were on duty or on standby.

The inauguration was witnessed on television by a massive global audience and ushers in a new era of American politics.