Making his inaugural speech as the US President, Barack Obama has said that "America is friend of all nations and we are ready to lead once more."

"Time has come to set aside our childishness...We must begin the work of remaking America," he said. "The challenges we face are real but they will be met."

"A country cannot prosper if it only supports the prosperous. Our nation is at war; our economy is badly weakened," he said.

"America is bigger than the sum of our individual aspirations. Our spirit is stronger and no one can outlast us."

Obama made a most significant remark about Iraq: "We will leave Iraq to its people," he said.

Earlier, Obama took oath as the 44th President of the United States. The oath was administered by the Chief Justice of the United States. Joe Biden was sworn-in as the Vice-President.

To witness the historical moment, millions gathered in Washington DC. Crowds thronged Pensylvania Avenue near the White House and along the National Mall in front of the Capitol Hill where Obama took oath.

Former Presidents Jimmy Carter, George H W Bush, Bill Clinton and outgoing President George W Bush attended the ceremony.