U.S. Chief Justice John Roberts has administered the oath of office to President Barack Obama for a second time to make up for misplacing a word during Tuesday's inauguration ceremony.
Mr. Obama re-took the oath of office at the White House late Wednesday, acting out of what a White House statement said was "an abundance of caution."
President Obama spent his first full day in office addressing some of the toughest issues facing the country - the financial crisis and the wars in Iraq and Afghanistan.
Mr. Obama held talks with his economic advisers and with Defense Secretary Robert Gates and other military advisers.
Mr. Obama has vowed to withdraw troops from Iraq within 16 months. He supports a plan to nearly double the U.S. troop presence in Afghanistan.
On the economy, the president is pushing for an $800 billion plan aimed at saving or creating millions of jobs.
Earlier Wednesday, Mr. Obama announced a pay freeze for senior White House employees, saying American families are being careful with their money, and so should Washington. He also said "transparency and the rule of law" will be the basis of his administration, in announcing rules concerning former lobbyists who join the government.
More than a million people turned out Tuesday on the National Mall in Washington to witness Mr. Obama's inauguration as the 44th president of the United States, and the nation's first African-American commander-in-chief.