Barack Obama says regrets Liu Xiaobo can't attend Nobel ceremony

US President Barack Obama said on Friday he regretted that neither Chinese dissident Liu Xiaobo nor his wife would be allowed to attend the ceremony in Oslo awarding Liu the Nobel Peace Prize and urged China to do more to advance democracy.

Obama also said Liu should be released from jail as soon as possible.

"America respects the unique culture and traditions of different countries," Obama said in a statement. "We respect China's extraordinary accomplishment in lifting millions out of poverty, and believe that human rights include the dignity that comes with freedom from want. But Mr Liu reminds us that human dignity also depends upon the advance of democracy, open society, and the rule of law."

China jailed Liu last Christmas Day for 11 years for subversion of state power and for being the lead author of Charter 08, a manifesto calling for democratic reform in the one-party state.

Obama made reference in the statement to his own attendance with his wife Michelle at the ceremony in Norway last year when he was awarded the Nobel Peace Prize.

"I regret that Mr Liu and his wife were denied the opportunity to attend the ceremony that Michelle and I attended last year," he said.

"The values he espouses are universal, his struggle is peaceful, and he should be released as soon as possible."