"He still has potential to improve, but not much," Sun told reporters after a training session at the Al-Arabi Sports Club in Doha.

"We hope to save the best for the 2008 Olympic Games," he added.

Sun said he has begun to adjust his training regime in order to tap Liu's full potential.

"I am gradually increasing his training load," he said.

Liu, who shattered the world record when he clocked 12.88 seconds at an IAAF meet in Lausanne in July this year, is looking to round off his sizzling season in style with a second Asian Games gold. Four years ago, he scored a runaway victory in the 110m hurdles, clocking a Games record of 13.27 in Busan, bettering compatriot Li Tong's 1994 mark of 13.30.

Sun predicted that Liu would clock a time of around 13.20 in Doha.

"That time would be good enough to break his own Asian Games' record," said Sun.

"Liu could run faster than 13.20 if he goes all out. But at this moment, it is unnecessary and unwise to take risks.

"Our priority here is to avoid being injured. Then comes the goal of winning the gold medal and breaking the Asiad record."

After Japan's Olympic hammer champion Koji Murofushi and host Qatar's world champion steeplechaser Saif Saeed Shaheen pulled out with injuries, the 23-year-old Liu is the most shining star in theGames' track and field events, which will start Thursday at Khalifa stadium.