Obama gives himself B+

US President Barack Obama on Sunday awarded himself a B plus for his first 11 months in office, stressing in an interview with talk show queen Oprah Winfrey that there was still much to be done.

"A good solid B plus," Obama said during an hour-long, intimate soft-focus ABC network Christmas at the White House special, when Oprah asked what grade he would give himself.

Explaining why he wouldn't give himself top marks, the president said his administration had "inherited the biggest set of challenges of any president since Franklin Delano Roosevelt" which they were still working on.

He had earned good points for helping to stabilize the economy, setting a path out of Iraq and restoring America's international image, but the job was not yet finished.

"B plus because of the things that are undone. Health care is not yet signed. If I get health care passed, we tip into A minus," Obama said, his hair visibly grayer than when he took office on January 20.

Oprah was given an inside tour of the White House by First Lady Michelle Obama, wearing a knee-skimming, long-sleeved simple plum dress.

They inspected the decorations and trees adorning every nook and cranny of the nation's most exclusive address, and which have taken most of the year to plan.

Pride of place went to a huge Christmas tree in the Blue Room hung with more than 650 baubles collected from around the White House closets and then sent around the country for people to decorate by hand with local scenes.

And there was also the 350-pound (160 kilo) gingerbread White House in the dining room, smothered in white chocolate with a model of Bo, the family dog, sitting by the steps.

Michelle Obama acknowledged that Portuguese waterhound Bo, who showed Oprah that he can "High-five" with his paw, would have his own stocking hanging up for Santa.

"Santa loves Bo too," the first lady exclaimed, as she revealed officially that the family would be spending the Christmas holidays in Hawaii where the president spent much of his childhood.

Obama said that if he had a seasonal wish it was: "I want the American people to feel confident that our future is gonna be bright.

"The 21st century will be as much the American century as the 20th century, as long as we maintain our sense of unity, but also our sense of hard work and determination," the president added.