Barack Obama on Tuesday pledged to "remake America" after he was sworn in as the 44th president of the United States on the west front of the Capitol in Washington D. C..

"Starting today, we must pick ourselves up, dust ourselves off, and begin again the work of remaking America," Obama told an unprecedentedly massive audience filling up the National Mall in the capital.

"For everywhere we look, there is work to be done. The state of the economy calls for action, bold and swift, and we will act -- not only to create new jobs, but to lay a new foundation for growth," he said.

Then the first African-American president outlined his to-do list.

"We will build the roads and bridges, the electric grids and digital lines that feed our commerce and bind us together. We will restore science to its rightful place, and wield technology's wonders to raise health care's quality and lower its cost. We will harness the sun and the winds and the soil to fuel our cars and run our factories. And we will transform our schools and colleges and universities to meet the demands of a new age, " he said.

"All this we can do. And all this we will do," the president noted.

Obama acknowledged the daunting challenges facing the nation, saying "we are in the midst of crisis is now well understood."

"Our nation is at war, against a far-reaching network of violence and hatred. Our economy is badly weakened, a consequence of greed and irresponsibility on the part of some, but also our collective failure to make hard choices and prepare the nation for a new age. Homes have been lost; jobs shed; businesses shuttered. Our health care is too costly; our schools fail too many; and each day brings further evidence that the ways we use energy strengthen our adversaries and threaten our planet."

But the president said although the challenges "are real" and " will not be met easily or in a short span of time," America's goals "will be met."

"Our challenges may be new. The instruments with which we meet them may be new. But those values upon which our success depends -- hard work and honesty, courage and fair play, tolerance and curiosity, loyalty and patriotism -- these things are old. These things are true," he said.

"This is the source of our confidence -- the knowledge that God calls on us to shape an uncertain destiny," said Obama.

Barack Obama swears in as the 44th president of the United States of America in front of the U.S. Capitol in Washington D.C. Jan. 20, 2009. [Xinhua/Zhang Yan]

Obama took the oath before John Roberts, chief justice of the Supreme Court.

Placing his hand on the same bible used by Abraham Lincoln to take the oath of office, Obama repeated the oath of office of all his predecessors:

"I do solemnly swear that I will faithfully execute the Office of President of the United States, and will to the best of my ability, preserve, protect and defend the Constitution of the United States. So help me God."

Obama began his inaugural speech by paying tribute to U.S. ancestors and outgoing President George W. Bush.

"I stand here today humbled by the task before us, grateful for the trust you have bestowed, mindful of the sacrifices borne by our ancestors. I thank President Bush for his service to our nation, as well as the generosity and cooperation he has shown throughout this transition," he said.

Barack Obama said that the country will seek "even greater cooperation and understanding between nations" under his new administration.

Obama called for "a new way forward" in developing relations with the Muslim world.

"To the Muslim world, we seek a new way forward, based on mutual interest and mutual respect," he said.

Obama pledged to help the poor nations and urged the rich to discard their "indifference."

"To the people of poor nations, we pledge to work alongside you to make your farms flourish and let clean waters flow; to nourish starved bodies and feed hungry minds," Obama said immediately after his presidential inauguration at the U.S. Capitol, as people around the world were listening.

"And to those nations like ours that enjoy relative plenty, we say we can no longer afford indifference to suffering outside our borders; nor can we consume the world's resources without regard to effect," he said.

Despite clod weather, an unprecedentedly massive crowd is gathering in Washington to witness the historic inauguration of Obama, surely to break the historic record of 1.2 million people attending the inauguration of Lyndon Johnson in 1965.

According to official estimate, as much as 2 million people are gathering around the Capitol, White House and Lincoln Memorial when Obama took oath of the office.

U.S. President George W. Bush greets U.S. President-elect Barack Obama (L) on the North Portico of the White House in Washington, January 20, 2009. First lady Laura Bush is second from left, and Michelle Obama is at right. [Reuters]

The president and his family, after a 40-minute coffee break at the White House, were accompanied to the U.S. Capitol by outgoing President George W. Bush. This was also the last time for Bush to leave the White House as the U.S. president.

Amid tight security, the flag-bearing motorcade, carrying the present and future leaders of a nation reeling from a crippled economy and two wars, passed jubilant and cheering well-wishers who lined the streets.

Editor: Yan