Liu Xiang's disqualification from the Prefontaine Classic after a one-two Chinese false start Sunday underscores a disappointing US trip in the run-up to the Beijing Games.

The Olympic and world champion returns to his native China this week after a two-week trip to North America where he pulled out of one race and was disqualified from the other.

Liu was disqualified after posting the second false start in the 110 metre hurdles on Sunday in front of a crowd of about 13,500 at the University of Oregon track.