Former US president Obama makes 'Santa' debut!

• He wore the cap and carried a bag full of gifts.

Former US president Barack Obama took on a new high-profile role as Father Christmas on Wednesday for a surprise visit to sick children in Washington.

Sporting a festive Santa hat and armed with a sack of gifts, he delighted young patients at Children's National hospital with gifts and hugs.

"I just want to say thank you to all of you guys," Obama told staff, who greeted him with rapturous cheers, in a video he shared on his Twitter account.Thank you @BarackObama for making our patients' day so much brighter. Your surprise warmed our hallways and put smiles on everyone's faces! Our patients loved your company.and your gifts!

"We've had the chance to talk to some of the wonderful kids and their families," he added.

"As the dad of two girls, I can only imagine in that situation to have nurses and staff and doctors and people who are caring for them, and looking after them... that's the most important thing there is."

The 44th president of the United States still lives in Washington, where he last year dressed up as Santa to visit middle school students at a Boys & Girls Club in the capital.