Chinese star hurdler Liu Xiang has publicly apologized for letting the nation down after he quit the Olympics due to an injury but also vowed to stage a comeback.

Liu, 25, World and Olympic champion, pulled out of the 110m hurdles qualifying heats because of a worsened tendon injury in his right foot, dashing China's only gold hope in Olympic track.

"So many people have been worried and caring about me.

"I feel sorry.

"I could do nothing but pull out of the race," Liu said.

"I didn't feel right when I was warming up before the race," said Liu.

I felt painful when I was just jogging," he added.

Liu though vowed to make a comeback and said he is a man who never easily quits.

"I never quit easily.

"I believe I will come back," Liu said.

Many of his fans present at the stadium were seen sobbing at the sight of a limping Liu.

Chinese athletics head coach Feng Shuyong said: "Liu was depressed."