American President Barack Obama took the oath of office on Sunday to begin his second term.

The ceremony was simple and empty of the hope and historic promise that greeted his inauguration four years ago.

Obama will retake the oath in public at the US Capitol: "I, Barack Hussein Obama, do solemnly swear to faithfully execute the office of President of the United States and to preserve, protect and defend the Constitution of the United States."

Obama, with a slight smile, took the oath with his right hand raised, and his left on a family Bible held by his wife Michelle, wearing a blue dress, to match the decor of the oval White House Blue Room hosting the ceremony.

Chief Justice John Roberts read each line of the oath out loud, before the president repeated phrases first intoned by George Washington 224 years ago.

Watched over by portraits of other former US leaders, including Thomas Jefferson and John Adams, Obama hugged his wife and children Malia, 14, and Sasha, 11, before quipping: "I did it" to his youngest daughter.

Michelle Obama later sent a personal tweet saying: "Barack just took the official oath at the @WhiteHouse & used my grandma's bible for the ceremony. I'm so proud of him. — mo."

The president said the celebrations were also a reminder there was something larger than the individual and praised the "decency, the goodness, the resilience, neighborliness, the patriotism, the sense of duty, the sense of responsibility of the American people."

Obama, 51, will embark on a second term at a time of deep partisan division in Washington, and will face foreign crises testing his legacy, including Iran's nuclear program and resurgent Islamist militancy in North Africa.

Tradition states that when that date falls on a Sunday, a private swearing-in is followed on Monday by the public festivities, including the second oath taking, the address, parade and glittering inaugural balls.