Defending Olympic champion Liu Xiang pulled out of the men's 110m hurdles first round Monday morning at the Beijing Olympics.

In the last heat of the first round, Liu quit the race after a false start of Dutchman Marcel van der Westen. He limped off the track, obviously being troubled by a foot injury.

Liu's coach Sun Haiping said in a post-race press conference, "His right heel injury has been a long problem since six years ago, even before the Athens Olympics."

"On Aug. 16, we arrived at the Olympic village, medical experts analyzed Liu's injury and specified there was a problem on Liu's Achilles's tendon," Sun said.

World record holder Dayron Robles of Cuba earlier breezed through to the next round, clocking 13.39 seconds.

He said, "I'm perfect today, and the track is good for breaking world record."

Without Liu and Olympic silver medalist Terrence Trammell of the United States, who fell down to the track in heat five, Robles will be almost unbeatable in the finals.

Liu's teammates Shi Dongpeng and Ji Wei were also qualified for the next round.

China's Liu Xiang reacts prior to the first round competition of men's 110m hurdles at the National Stadium, also known as the Bird's Nest, during Beijing 2008 Olympic Games in Beijing, China, Aug. 18, 2008. The defending champion Liu Xiang dropped out after getting injury. (Xinhua/Li Gang)

China's Liu Xiang reacts prior to the first round competition of men's 110m hurdles at the National Stadium, also known as the Bird's Nest, during Beijing 2008 Olympic Games in Beijing, China, Aug. 18, 2008. The defending champion Liu Xiang dropped out after getting injury. (Xinhua/Li Gang)

China's Liu Xiang kneels down while warming up prior to the first round competition of men's 110m hurdles at the National Stadium, also known as the Bird's Nest, during Beijing 2008 Olympic Games in Beijing, China, Aug. 18, 2008. The defending champion Liu Xiang dropped out after getting injury. (Xinhua/Liu Yu)