US swimmer Michael Phelps reacts to setting a new world record in the Mens 100m Butterfly at the USA Swimming National Championships in Indianapolis. -Reuters

INDIANAPOLIS Michael Phelps broke the world record in the 100-meter butterfly at the US championships on Thursday.

The 14-time Olympic gold medalist swam the two-lap final in 50.22 seconds at the Indiana University Natatorium. He lowered Ian Crockers mark of 50.40 set at the 2005 world championships in Montreal.

Phelps led at 50 meters with a split of 23.83, just three-tenths off world-record pace. Known for his strong finishes, he pulled clear to beat Tyler McGill, who touched in 51.06. Aaron Peirsol was third in 51.30.

Phelps had once owned the 100 fly mark for a day at the 2003 worlds in Barcelona. But Crocker took it from him a day later, then lowered it twice more.

I still remember the day at worlds when I broke it and the next day Crock broke it and Crocks had it ever since, he said. To finally be able to get it tonight means a lot.

Phelps victory gave him a spot in the event at the world championships this month in Rome. He already qualified in the 200 fly and 200 freestyle as he continues his transformation from swimming middle distances to sprints. -AP