PHILADELPHIA, Pennsylvania (AFP) - World 100-meter record holder Asafa Powell and treble world champions Tyson Gay and Allyson Felix lead a host of stars into Saturday's "USA versus the World" Penn Relays showdown.

Nearly 150 athletes from 11 nations will compete in the annual elite session of the meet, which the Americans have dominated in the past three editions, winning five of the six races each time.

The meet features 4x100, 4x400, women's sprint and men's distance relays and will serve as an early test ahead of August's Olympic meet in Beijing.

Powell, 25, set the 100m world record of 9.74 seconds last September in Italy and will be joined by several fellow Jamaicans.

Michael Frater, the 2005 world 100m runner-up, will join countryman Powell as will 2004 Olympic 4x100m gold medalist Sherone Simpson, 2000 Olympic 4x400m bronze medalists Sanjay Ayre and Michael Blackwood and world relay veterans Novlene Williams and Shericka Williams.

The formidable American men are paced by Gay, a triple champion at last year's world meet, reigning Olympic and two-time world 400m champion Jeremy Wariner and 2007 world 400m hurdles champion Kerron Clement.

The US lineup also includes two-time world 200m medalist Wallace Spearmon, 2007 world 400m runner-up LaShawn Merritt and Darold Williamson, a member of the 2004 Olympic 4x400m relay winners.

Felix will be joined on the US women's side by 2006 IAAF Athlete of the Year Sanya Richards, 2005 world 100m champion Lauryn Williams, 2003 world 100m champion Torri Edwards, two-time world 100m hurdles champion Michelle Perry and 2005 world 400m runner-up Lashinda Demus.