INDIANAPOLIS: Olympic swimming star Michael Phelps launched his World Championship bid on Wednesday with the fastest qualifying times in the 200m free and 200m butterfly at the US championships.

Phelps clocked 1min 46.31sec to book his berth in the 200m freestyle finals, with Peter Vanderkaay second-quickest after winning his heat in 1:46.42. David Walters was third-fastest overall after finishing second to Phelps in their heat in 1:46.46 and Ryan Lochte was fourth-quickest in 1:46.51.

Both Vanderkaay and Lochte will be seeking their second titles of the meet. Vanderkaay won the 400m freestyle on Tuesday and Lochte won the 400m individual medley, booking their berths on the US team for the World Championships in Rome later this month.

Phelps was idle on Tuesday as he waited to begin a four-event programme that also includes the 100m freestyle and 100m butterfly.

"It was all right," Phelps said of his morning's work, adding that he felt better in the 200 fly than in his opening 200 free. He owns the world record in both events - both set in winning gold in Beijing.

Just 1.5sec separated Phelps from the No.8 qualifier in the 200m free, Daniel Beal, who booked his berth in the final with a time of 1:47.81.

Phelps led the way into the 200m fly final with a time of 1:55.36.

The 24-year-old American again distanced himself from the furore surrounding the controversial new super-suits linked to a wave of world records this year, reiterating he plans to stick with the Speedo LZR Racer.

"I'm here to swim, not to talk about the suits," Phelps said.

He will make one change however, opting for a full-body suit for the final of the butterfly, a stroke in which he previously preferred an LZR style that left his upper torso uncovered.

"I tried it out in Montreal and I liked it," said Phelps, who flirted with the 100m fly world record at the Canada Cup with a personal best time of 50.48sec on June 20. "That was a fairly good swim."