A US team stung by two high-profile injury absences and a late doping case still sends a squad with eight reigning title holders to a 2011 World Championships seen as a springboard to 2012 Olympic success.

The loss of injured sprinter Tyson Gay and 400m star Jeremy Wariner were undoubtedly blows to an American squad trying to reassert its dominance over Jamaica in the sprints and match, if not improve on, its haul of 22 medals - 10 of them gold - at Berlin in 2009.

Gay's injury withdrawal from the US trials robbed the US of the American reckoned most likely to challenge Jamaican sprint superstar Usain Bolt.

The Americans suffered another blow when Michael Rogers, who recorded the fourth-fastest 100m time of the season, tested positive for a banned stimulant and withdrew from the championships as he accepted a provisional ban until his case is concluded.

Walter Dix, who won the 100m and 200m at the US championships, now spearheads a group of US men sprinters that also includes Justin Gatlin, who has returned from a four-year doping ban to earn a 100m berth, veteran Darvis Patton and Rodgers' replacement, Trell Kimmons.

"I think we have a good combination, a good balance of veterans and youth," men's head coach Vin Lananna said at the conclusion of the US trials in June.

"I think the United States is in a great position for the championships in Daegu and also in setting the table for what's to happen in London a year from now."

Things look brighter for America's women sprinters, with Carmelita Jeter the top performer this year at 100m and hungry for a first major international gold. Jeter will also chase 200m gold, as will season-leader Shalonda Solomon and three-time defending champion Allyson Felix.

Felix, however, will enter uncharted territory in Daegu as she bids for a 200m-400m double. She has admitted she doesn't know how her pursuit of the 400m before the 200 will affect her in the event she has dominated for so long.

"I feel like mentally I am going to take one round at a time and physically I feel like I have done the work in practice and I just have to sustain my body the best I can throughout the competition," she said.

In the 400m, Felix will be up against reigning title holder Sanya Richards-Ross, runner of the second fastest time this year.

LaShawn Merritt, back from a doping ban of almost two years, will defend his 400m title.

"At the worlds, I will be a contender," Merritt vowed after finishing second to Jamaica's Jermaine Gonzalez in his return to the track in July in Stockholm, where he clocked 44.74sec. Tony McQuay is the top American in the 400m this season.

David Oliver boasts the top time in the 110m hurdles this season, but with a field expected to include 2008 Olympic champion Dayron Robles of Cuba and former world record-holder Liu Xiang of China no one is a sure thing.