Liu Xiang of China grimaces in pain during his warm-up before the start of his 110m hurdles heat of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 18, 2008. [Agencies]

BEIJING - Liu Xiang, China's great hope for track glory at the Beijing Games, said he was sorry for his surprising withdrawal from the Olympics but that he had no choice because pain from a foot injury became unbearable.

"There are so many people concerned about me and supporting me. I feel very sorry. But there's really nothing I could do," a disconsolate Liu told China Central Television in an interview aired Tuesday.

A day earlier, Liu withdrew from his heat in the 110-meter hurdles, shocking and disappointing millions of Chinese who wanted to see him defend his Olympic title at home.

Liu appeared pale and tired, wearing a plain white T-shirt rather than the flashy red that has characterized the uniform of China's athletes at the games. A drop of perspiration clung to the corner of his left eyebrow as he spoke in a steady voice against a white background.

The 25-year-old Liu won China's first men's Olympic gold medal on the track in Athens four years ago, and became a superstar to rival NBA hero Yao Ming at home and a posterboy worth millions for the Beijing Games. His surprise withdrawal on Monday shocked China. His coach was among those who wept openly.

Vice-president of China Xi Jinping sent a message of support to Liu Monday night.

"I didn't feel right when I was warming up before the race," Liu said, in Xinhua's translation of his comments. "I knew my foot would fail me. I felt painful when I was just jogging."

He talked about running a competitive time just two weeks ago.

"I didn't know why things turned out this way," he said. "I wanted to hang on. But I couldn't. It was unbearable. If I had finished the race, I would have risked my tendon. I could not describe my feeling at that moment."

Speculation swirled for weeks that Liu was injured, and he trained in seclusion before he first appeared at the Bird's Nest on Monday.

In his warmup, Liu grimaced through clenched teeth and limped gingerly after clearing two hurdles, but took to the blocks anyway for the first heat of the event for which he was the favorite.