Colorado - Italy's Elia Viviani surged ahead in the final metres to win Friday's fourth stage of the USA Pro Cycling Challenge while American Levi Leipheimer kept the overall lead.
Viviani, a 22-year-old second-year rider for Liquigas, completed the 133.25km stage from Avon to Steamboat Springs in 2 hours, 58 minutes and 14 seconds.
Danish rider Michael Morkov of Saxo Bank was second in the stage with Dutchman Kenny Robert Van Hummel of Skil-Shimano finishing third.
Leipheimer, who rides for US RadioShack, kept the 11-second overall lead he seized by winning stage three Thursday. Christian Vande Velde of Garmin-Cervelo remained second overall after finishing 21st in stage four.
Tejay Van Garderen of HTC-Highroad was third, 17 seconds behind Leipheimer, four seconds in front of Tom Danielson of Garmin-Cervelo with George Hincapie of BMC in fifth, 53 seconds adrift, as Americans owned the top five spots.
Australian Cadel Evans of BMC, who won last month's Tour de France, remained seventh, 78 seconds off the pace, after finishing 27th in Friday's stage.