London, Aug 2 South African Chad le Clos sounded out a warning to Michael Phelps that he will again be the man to beat if the American wants to retain his Olympic title in the 100 metres butterfly.

Le Clos scored a dramatic last gasp victory over Phelps to take gold in the final of the 200 metres earlier this week and was the fastest swimmer in the heats for the 100m event, qualifying for the semi-finals with a time of 51.47, 0.18 seconds ahead of Phelps who took the second fastest time, reports Xinhua.

China's Zhou Jaiwei made it to the semis with the eighth fastest time, while Le Cros was at pains to play down his win.

"I don't think so. It is too short for me. I am just trying for a fast time that will get me into the final. These guys will be a lot quicker (in the semi-finals) than they were this morning," he replied when asked whether he could repeat his triumph over Phelps in the event.

Phelps was slightly worried that he will compete in the 200 medley final just 35 minutes before the semi-final.

"It doesn't really add too much time for rest purposes tonight if I'm in the first or the second one (semi-final). We just wanted to come in and get a good morning swim, so that was fun," he commented.

© IANS