SYDNEY, Australia — Eamon Sullivan has broken his own world record in the 50-meter freestyle, setting a second mark in 24 hours at the Australian swim championships and Olympic trials.

It was the fourth time in the past six weeks that the record has been broken after Russian Alexander Popov's record stood for nearly eight years. The 22-year-old Sullivan has broken it three times.

Sullivan clocked 21.28 seconds in the final today, after lowering the mark to 21.41 in the semifinals yesterday.

His semifinal broke the 21.50 set by France's Alain Bernard at the European championships last weekend.

Bernard broke Sullivan's mark of 21.56 set Feb. 17 in the same pool.

Popov's 21.64 came in Moscow on June 16, 2000.