Phelps won the race by more than six seconds

Phelps, who won six Olympic golds in 2004, clocked one minute 53.71 seconds to shave nine hundredths of a second off his previous mark set last August.

The 21-year-old has broken the record five times and will aim to make it six at next month's World Championships.

"When I saw the time my reaction changed and I basically went nuts. I did not expect that," said Phelps.

"I didn't think I was going to break a record but I could tell something good was happening when I heard the crowd."

He put his performance down to hard training.

"A lot of our practice has been focused on underwater kicking, and I know that the more kicking I do, the faster I can go.

"Coming off the wall well when people are getting tired is a good weapon to have. We have wanted to work on it and it's starting to show now." he said.