Updated

Ryan Lochte and Michael Phelps will have their first showdown on the opening night of the U.S. Olympic swimming trials.

The world's top swimmers advanced to Monday's final of the 400-meter individual medley, a loaded race that also includes the silver medalist from last year's world championships, Tyler Clary. Only the top two earn a spot on the team for London.

Lochte, the defending world champion, was the top qualifier in morning preliminaries with a time of 4 minutes, 10.66 seconds. Phelps was next fastest, cruising through his preliminary heat in 4:14.72. Clary was fourth-fastest at 4:15.88.

Phelps is the world-record holder and won the 400 IM at the last two Olympics, but he vowed to drop the grueling event after Beijing. He brought it back over the past year and said he's known "for a while" that he would be in the race at Omaha. The only stumble came beforehand, when Phelps realized he had the wrong cap. He found a plain white model that worked just fine.

"It felt fairly relaxed," said Phelps, a 14-time Olympic gold medalist who plans to retire after these games. "I'm happy."

Lochte was pleased with his effort, though he knows he'll need to go even faster to beat Phelps. He expects his rival to put in a much better time in the evening.

"That was the easiest 4:14 he's ever done, that I've seen in the whole entire world," Lochte said. "It looked really, really smooth for him. Tonight's definitely going to be a dogfight. It's not just going to be me and Michael. It's going to be Tyler Clary, too. It's definitely going to be a fight."

Brendan Hansen, who quit the sport after two straight disappointing Olympics but decided to come back for the London Games, advanced in the 100 breaststroke with the second-fastest time.

"Just get that first one under your belt — that's what I wanted to do," said Hansen, whose time of 1:00.30 was a hundredth of a second behind lead qualifier John Criste. "It was a little rough. But I've been feeling great in the water, and I'm just going to get faster with every swim."

Also advancing to the evening semifinals was Eric Shanteau, who competed in Beijing after being diagnosed with testicular cancer.

Phelps' coach, Bob Bowman, was coy about his plans before the trials but said he's known since a March meet in Indianapolis that Phelps was going to compete in the 400 IM.

"He did one and it's really the best one he's ever done in a season," Bowman said. "He was like, 'Man, it would be a shame not to do this.' We'll know a lot more tonight whether that was a good decision."

Clary expected Phelps to scratch from the event, which would have made it much easier to qualify for a spot on the Olympic team. Now, Clary has to beat either Lochte or Phelps to compete in the 400 IM in London.

"It will definitely be a more interesting race now," Clary said, managing a slight grin. "All I can do is control myself. It doesn't matter to me who's in the heat. I'm going to go out and swim the race that I've got in my mind. I think that'll be good enough."

Lochte is eager to face Phelps as many times as possible in Omaha before they resume their rivalry in London.

"Of course, I want to win," Lochte said. "I hate not winning. I love to win. But if it doesn't happen, it doesn't happen. I'm not going to beat myself up over it."

Dana Vollmer, coming back from the disappointment of missing the Olympics four years ago, was the top qualifier in the 100 butterfly. She posted the fastest time ever in the United States (56.59), breaking a 12-year-old mark, and has her sights on Sarah Sjoestroem's world record (56.06), which was set in 2009 during the era of high-tech, rubberized suits.

"It's always in the back of my mind," said Vollmer, the defending world champion in the 100 fly. "I definitely want to do a 55."

Vollmer, who made the 2004 Olympics as a 16-year-old, battled injuries and medical problems for much of the past decade, but she's healthy now and thriving with a new diet.

"I feel better than I did at worlds," she said. "That race felt good, but I still feel like I didn't put all I have into it knowing it's just the prelims. To be at that time, it's definitely a good sign for my next swims."

Elizabeth Beisel led qualifying in the women's 400 IM at 4:35.72, nearly 4 seconds ahead of Caitlin Leverenz. Connor Jaeger was fastest in preliminaries of the men's 400 freestyle (3:48.06), with two-time Olympian Peter Vanderkaay also claiming a spot in the evening final.

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