In a moment of genuine historical significance, Barack Obama was sworn in as the first black President of the United States today.

With one hand on Abraham Lincoln's inaugural Bible, the 47-year-old son of a Kenyan father and white American mother pledged the Oath of Office before a hopeful nation and a global audience of billions.

In becoming the 44th president of America he also inherited a country in deep recession, with rising unemployment and an army fighting wars in two countries.

President Obama invoked the struggle and sacrifice of America's pioneers as he vowed to meet the challenges that now face him.

Shortly after being sworn in as the first black president of the United States, Mr Obama said that in his election, America had chosen "hope over fear, unity of purpose over conflict and discord".

But he acknowledged that the country was in "the midst of crisis", with a weakened economy and at war "against a far-reaching network of violence and hatred".

Mr Obama took the Oath of Office shortly after midday local time on the west front of the Capitol building in Washington.

The ceremony was held in front of a waiting world and an audience in the National Mall numbering more than one million people.

All wanted to witness the moment of genuine historic significance.

They were forced to wait... the swearing-in of Mr Obama was later than expected, taking place shortly after 12pm.

After being sworn in by chief justice John Roberts, Mr Obama made his first speech as president.

He said: "The challenges we face are real. They are serious and they are many. They will not be met easily or in a short span of time.

"But know this, they will be met."