BRUSSELS, Belgium -- Lance Armstrong, his Discovery Channel cycling teammates and a leading pack were left gasping Sunday as Belgian Tom Boonen launched a stunning one-man breakaway to win the Tour of Flanders.

Boonen, racing for Quick.Step, broke away from the leaders with only a few miles left in the race, opening a 35-second lead over his nearest rival, Andreas Klier, a German racing with T-Mobile.

The Discovery squad included Tony Cruz, Stijn Devolder, Viatscheslav Ekimov, George Hincapie, Leif Hoste, Roger Hammond, and Hayden Roulston – as well as Armstrong.

Discovery riders interviewed before the race said their two primary riders were Devolder and Hincapie, but their goal was to swarm the finish with as many riders as possible, according to Armstrong's official Web site.

Hincapie, who has looked strong all spring, placed seventh on the 159-mile course, a minute behind Boonen. Armstrong supported Hincapie up until the last 15 miles of the hilly course, which features long stretches of cobblestone..

Discovery director Johann Bruyneel told the Associated Press on Sunday that he was satisfied with Armstrong's performance on Sunday.

The Texan "suffered," Bruyneel said, but added that Armstrong was still on course for a record-stretching seventh Tour de France title in July.

Armstrong has scheduled a press conference for April 18 for what is being billed as a major announcement about his career. He is scheduled to race the next day in the 5-day Tour of Georgia, his only scheduled U.S. race this year.

Bruyneel brushed aside speculation that Armstrong was going to announce his retirement, according to a story Sunday on the Velo News Web site.

On Saturday, Armstrong fired back against new drug allegations. The Texan has filed court documents seeking at least $125,000 from Mike Anderson, who contends he found a banned substance in the cycling champion's apartment last year. Anderson worked for Armstrong for about two years and has said the cycling great had promised to help him start a bike shop. His claims were in a brief filed Thursday.