Phelps has recently returned from a three-month ban
Olympic superstar Michael Phelps has broken the 100m butterfly world record.
The 24-year-old American, who has won 14 Olympic gold medals, lowered countryman Ian Crocker's four-year-old mark of 50.40 seconds, clocking 50.22.
The win at the US trials in Indianapolis secures Phelps a place in the 100m butterfly at the World Championships in Rome later this month.
"I really wanted to break 50 seconds but that is something to shoot for," said Phelps.
"Ian Crocker texted me after prelims. He wished me all the luck. That really meant a lot to me as a competitor and as a friend."
Phelps has recently served a three-month ban after he was pictured apparently smoking cannabis.
Thursday's success takes his current tally of world records to five, along with the 200m freestyle, 200m butterfly and the 200m and 400m individual medley.
He won the 100m butterfly at both the 2004 and 2008 Olympics, but had been unable to snatch Crocker's record.
Phelps became the most successful Olympian in history when he won eight gold medals in Beijing last August to add to the six he claimed in Athens four years previously.
Tyler McGill was second in 51.06, with Aaron Peirsol third in 51.30.