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]

US President Barack Obama took oath of office a second time Wednesday at the White House because a word was out of sequence when he was sworn in Tuesday.

His oath taking was administered by Chief Justice John Roberts in front of reporters.

The oath was administered a second time out of an "abundance of caution", White House Counsel Greg Craig said in a statement.

"We believe that the oath of office was administered effectively and that the president was sworn in appropriately yesterday," he said.

"But the oath appears in the Constitution itself. And out of an abundance of caution, because there was one word out of sequence, Chief Justice Roberts administered the oath a second time," Craig added.

At his inauguration ceremony Tuesday, Obama stumbled as he swore to faithfully execute the office of president.

(Xinhua News Agency January 22, 2009)