Michael Phelps and Ryan Lochte set up their first duel at the US Olympic swimming trials on Monday as they qualified for the final of the 400m individual medley. Phelps, whose unprecedented eight gold medals at the Beijing Games gave him 14 Olympic titles, has won the event at each of the last two Olympics and still owns the world record of 4min 03.84sec that he set at the Water Cube in 2008. He clocked a sedate 4:14.72 to win his heat, while Lochte, the reigning world champion in the event, won his heat in 4:10.66. Lochte, however, said the four-second gap would mean nothing in Monday night\'s final. \"I think that\'s the easiest 4:14 he\'s ever done,\" Lochte said of Phelps. \"He looked really smooth. Tonight\'s going to be a dogfight -- and it\'s not just me and Michael, there\'s Tyler Clary, too.\" Clary, who claimed silver behind Lochte at last year\'s World Championships in Shanghai, won his heat in 4:15.88, the fourth-fastest time of the morning. Chase Kalisz, swimming next to training partner Phelps, was third-quickest in 4:15.78. Phelps didn\'t swim the 400m medley in Shanghai. After Beijing, he said he wouldn\'t swim the punishing event again in major international competition. Some solid performances at Grand Prix meetings this season, particularly a strong mid-season swim in Indianapolis in March, prompted him to reconsider. \"We\'ll know more tonight if it was a good decision,\" said Phelps\'s coach Bob Bowman. \"It was all right,\" Phelps said of his preliminary performance, noting it was about a second slower than the 4:13.43 he clocked in the heats of the 2008 Olympic trials. \"It felt fairly relaxed.\" Clary, who had said he expected Phelps to forego the event, now must beat either Phelps or Lochte to secure a London berth. Only the top two finishers in each event book tickets to the Games. \"It did come as a surprise, but it doesn\'t change my game plan going into tonight,\" he said. \"It will definitely be a more interesting race now.\" Dana Vollmer, keen to erase the disappointment of her disastrous 2008 trials, led the way into the semi-finals of the women\'s 100m butterfly in an impressive 56.59sec. Vollmer won the 100m fly world title at Shanghai last year, but in returning to Omaha she returned to the scene of bitter disappointment in 2008, when she finished fifth in the 100m fly and seventh in the 200m free and failed to make the Beijing team -- four years after she earned relay gold as a teenager in Athens. \"I knew coming into this meet I feel better than I did at worlds,\" Vollmer said. \"I knew I needed to get the first race in and I\'d be less nervous. It felt smoother and easier than I expected that time to feel.\"