China's star hurdler Liu Xiang's back injury, which forced him out of the London Diamond League 110 meters hurdles final, is "not serious", his long-time coach Sun Haiping said on Friday.

"Liu Xiang felt a little uncomfortable with his back after the heats," Sun said at south London's Crystal Palace stadium. "We decided to pull out of the final just for the sake of caution. "

It's the first time the Chinese hurdler has retired from a competition since his shock withdrawal from the Beijing Olympic Games due to an Achilles tendon injury.

Liu, who was expected to run in his final pre-Olympic event on his 29th birthday, carries the weight of China's track and field hopes as his fans expect a second gold medal to follow his victory in Athens eight years ago.

"I am still under a lot of pressure although I am away from home this time," he said on Thursday. "There is too much expectation from the fans."

The London Grand Prix should have been a perfect chance for him to warm up for the Olympics. Besides the weather, he could have raced against United States rivals Aries Merritt and Jason Richardson, two of his biggest threats at the Olympic Games.

Liu has been in good form this season, beating Merritt and Richardson in Shanghai and at the Diamond League meet in Eugene, Oregon, where he registered a wind-assisted 12.87 seconds.

He had cruised into the London final after winning his heat in 13.27 sec, but failed to take his place on the start line for the final.

Merritt defied the cool, overcast conditions to equal his own season's fastest time of 12.93. Richardson was second in 13.06 and another American, Ryan Wilson, was third in 13.18.

"The conditions were the same for all of us and this will be great preparation for the Olympics if the weather is like this," said Merritt.

"I got here just two days ago so I am a little under the weather as far as my sleeping patterns are concerned. So it's amazing that I am running this well, I can't be more excited.

"I have to do it when it counts - this means nothing if I can't do it at the Olympics."

Liu will remain in London to prepare for the Games. The men's 110m hurdles title will be decided on Aug 8 at the Olympic Stadium.

(China Daily 07/15/2012 page7)