Hundreds of thousands of people converged to attend the ceremony in the National Mall in Washington DC to watch their favourite leader Obama take the oath shortly after 1700 GMT.
Obama during his oath, which was administered to him by the Chief Justice John Roberts, placed is hand on a Bible and promised to 'preserve, protect and defend' the US constitution.
Barack Obama during his inaugural address followed by the swearing-in declared that he plans to begin the work of 'remaking America'. He reminded that world has changed and it's 'a new age of responsibility'.
Referring to the scale of his achievement at being the first black American elected to the White House, in a remark that gathered one of the biggest cheers of the speech.
"This is the meaning of our liberty and our creed... why a man whose father less than 60 years ago fight not have been served at a local restaurant can now stand before you to take a most sacred oath."
Obama stated that America is a friend of each nation and every man, woman and child who seeks a future of peace and dignity, and that we are ready to lead once more
"The challenges we face are real," the new president said while adding: "They are serious and they re many. They will not be met easily or in a short span of time. "But know this America - they will e met," the new President announced.
Obama said that he would strive to rebuild his nation's standing in the world, saying: "We are ready o lead once more."
Making an assertive and candid inaugural speech at the Capitol Hill, President Obama reminded the Americans about the economic crisis and foreign policy challenges facing the US.
Commenting upon the much talked about issue of the George Bush's "War on Terror", Obama said hat the United States "would responsibly leave Iraq to its people" and build "a hard-earned peace in Afghanistan."
Reminding the countrymen of the tough challenges faced by the United States at present, he said: We are in the midst of a crisis and our economy is badly week. But we have chosen hope over fear and unity over discord."
"Our spirit is strongest and no one can outlast us," Obama asserted.
Showing magnanimity to the outgoing President George W. Bush, Obama said: "I thank Bush for is service to the nation".
He reminded everyone at the gathering that " the nation is bigger than our individual ambitions."
In his concluding remarks in the inaugural address to the nation, Obama reminded the citizens of America that while the country faces new and different challenges, its people must now enter "a new era of responsibility".
Obama concluded his speech saying "May God bless us .and the God bless United States of America."
Obama's swearing-in ceremony was followed by Joe Biden's. The Chief Justice John Roberts administered oath of office to Joe Biden for the post of Vice President of the United States.&13;&13;