World record-holder Regan Smith clocked an impressive 58.18sec to win the 100m backstroke at the Pro Swim Series at Des Moines on Saturday, her second victory of the meet.

The 18-year-old sensation, who set the world record of 57.57 in leading off a relay for the United States at the 2019 World Championships, notched the second-fastest time of her career in the event and the sixth-fastest in history.

Former world record holder Kathleen Baker was second in 58.56 and world bronze medalist Olivia Smoliga was third in 59.25.

The trio look poised for a monumental battle at the US Olympic trials in June, when only two swimmers can qualify to race the event at the Tokyo Games.

"It's great because it is such a stacked and talented field," said Smith, who also owns the 200m backstroke world record. "The crowd here really felt it and I felt really hyped up and excited. It was just such a great field and it just makes me really excited to race. It’s nerve-wracking for sure but it’s important to use those nerves in a good way and fuel them into your race."

In other events on the final day of the meeting, Caeleb Dressel won the 50m freestyle in world-leading 21.51 seconds, his second win of the week after his triumph in the 100m butterfly.

Olympic champion and world-record holder Ryan Murphy won the men's 100m back in 52.79, with Jacob Pebley second in 54.45.

"It's a great start," Murphy said of completing a backstroke double as he looks ahead to the Olympic trials. "I think it’s good to get some realistic data points of actual races and we've definitely got some stuff to build off of. I'm really happy with where I'm at right now."