Michael Phelps has responded in the best fashion possible to outspoken Chad le Clos - beating the South African in the pool.

Just hours after Chad le Clos had won the men's 100 metres butterfly at the FINA World Championships, Michael Phelps set a faster time in San Antonio.

Phelps won the 100m butterfly at the United States National Championships in a time of 50.45 - the fastest time in that event since high-tech suits were banned in 2010 - with Le Clos only managing 50.56 in Kazan.

After claiming gold in Russia, Le Clos - who has been involved in a slanging match with Phelps over the past few months - claimed his American rival could "keep quiet now" but the Olympic Games legend responded perfectly in the water.

Until Phelps' performance in Texas on Saturday, he had failed to swim faster than 50.56 since 2009 when he set the world record of 49.82 in a high-tech suit.

"I just did a time that [Phelps] hasn't done in four years [sic], so he can keep quiet now," Le Clos said after winning the 100m butterfly final in Kazan.

Asked about Le Clos' comments, Phelps said: "I saw the times, I saw the comments.

"There are a lot of things I could say but I won't. I let what I do in the pool do all my talking and that's how I've always done things."

It could be that the 23-year-old South African, who beat Phelps in the 200m butterfly at London 2012 but finished second behind the American in the 100m, wishes had kept his own mouth shut now.