By Steve Keating

OMAHA, Nebraska (Reuters) - Newcomer Chase Kalisz edged Olympic champion Ryan Lochte to register the top qualifying time in the men's 400 meters individual medley on Sunday and set up the first showdown of the U.S. Olympic Swim Trials.

Kalisz, who trains with Michael Phelps under coach Bob Bowman in Arizona, woke up a sleepy Sunday morning soldout crowd at the CenturyLink Center when he beat Lochte to the wall in a time of four minutes, 11.86 seconds.

Lochte, the 2012 London Olympic champion who is more familiar with taking on his rival Phelps in the stamina event, will instead have to contend with the 22-year-old Kalisz, who is bidding for a place on his first Olympic team.

The 31-year-old American has rarely raced the event since grabbing gold in London but looked ready for the challenge coming home just 0.12 seconds back of Kalisz. He warned later that he had more in the tank for the evening final.

The men's 400m IM final will be the highlight of the opening day of the week-long competition with the top two finishers earning tickets to the Rio Olympics in August.

"My first race is always the worst one but that was smooth -- just a solid swim. I didn't press anything to full potential so I think there is a little juice left," Lochte said. "There has to be."

Olympic spots will also be up for grabs in the women's 400m IM and men's 400m freestyle.

Sarah Henry will take the top qualifying time of 4:36.93 into the women's 400 IM final but will be hard pressed to earn an Olympic berth in a tough field that includes Olympic silver medalist Elizabeth Beisel and Maya DiRado, the world silver medalist.

Zane Grothe was top qualifier in the men's 400m freestyle which is expected to come down to a duel between Conor Dwyer, who had the second fastest effort, and Connor Jaeger, who narrowly missed out on a medal at last year's worlds.

The women's 100m butterfly final on Monday also has the potential to offer up a mouth-watering final with Kelsi Worrell clocking 56.84, the fourth fast time in the event this year, in the morning heats followed by former world record holder Dana Vollmer in 57.50.

The men turned in some sizzling times in the 100 breaststroke heats, Kevin Cordes clocking 59.05 to become the second fastest in the event this year.

(Editing by Adrian Warner.)