After taking office in frigid temperatures on Tuesday, U.S. President Barack Obama acknowledged the challenges facing his nation, and pledged to lead the task of "remaking America."

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. [Zhang Yan/Xinhua]

Earlier on the day, Obama was inaugurated as the 44th president of the United States on the west front of the Capitol in Washington, D.C., becoming the first black president in the country's history.

In the beginning of his address just after his swearing-in, Obama said: "That we are in the midst of crisis is now well understood," listing war, economy, healthcare, home foreclosures, jobs, energy and other challenges.

"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," he said.

But Obama assured Americans that although "the challenges we face are real, serious many," and "will not be met easily or in a short span of time," America's goals "will be met."

"Starting today, we must pick ourselves up, dust ourselves off, and begin again the work of remaking America," the president told a massive jubilant audience at the inaugural ceremony.

"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, and then outlined his to-do list of domestic affairs.