Michael Phelps of the U.S. poses with his gold medal during the awards ceremony for the men's 200m individual medley swimming final at the World Aquatics Championship in Melbourne March 29, 2007. [Reuters]

The 21-year-old American wunderkind smashed his own world record in the men's 200 meters individual medley in Melbourne on Thursday, winning his fourth gold at the on-going World Championships.

"I am just happy to swim fast again and have my training work," said the eight times Olympic medallist after he twice defended his title in the event in a time of one minute and 54.98 seconds, slicing 0.86 seconds off the previous world record set by himself at the Pan Pacific Championships last August.

Phelps's teammate Ryan Lochte kept his pace well in the first three strokes, being dropped behind only in half-body length by the unmatched Phelps. But the silver medallist in the 100 meters backstroke faded in the last 50 meters of freestyle, finishing second in 1:56.19, 1.21 seconds behind Phelps.

Hungary star Laszio Cseh took the bronze by clocking 1:56.92, one step backward from the runner-up position two years ago.

Phelps clinched his first gold in Melbourne with the U.S. 4x100 meters freestyle relay team in the opening day's competition last Sunday. Then he triumphed in the 200 meters freestyle and 200 meters butterfly races both with world record smashing performances.

"I've said this before: anything is possible if you put your mind to it. I've had a good attitude and I've been successful. I'm going to stick to what works," said the prolific superfish.

The prodigy still has the 100 meters butterfly and the 400 meters individual medley to go. Besides, he might contribute for the U.S. 4x200 meters freestyle relay team on Friday.