China's Liu Xiang reacts after competing the heats of men's 110m hurdle during the star-studded Aviva London Grand Prix at the Crystal Palace in London, July 13, 2012. Liu pulled out of Diamond League London GP for back injury. [Xinhua/Wang Lili]

China's star hurdler Liu Xiang has pulled out the 2012 London Diamond League finals after suffering from a bad back.

Liu had cruised into the 110 meter hurdles final at Crystal Palace after winning his heat in 13-point-2-7 seconds, but was unable to take his place on the starting line after suffering back strain.

The final was won by American star Aries Merritt, who defied the cool, overcast conditions to equal his own season's best of 12-point-9-3seconds.