EUGENE, Oregon (AFP) - Fast as they are, world champion sprinters Tyson Gay and Allyson Felix cannot escape the spectre of doping that haunts the American athletics program here at the US Olympic trials.

US officials hope performances by Felix, Gay and others from Friday through July 6 will push aside the doping disgrace of Marion Jones, Antonio Pettigrew and others to help restore faith in a team and sport with crushed credibility.

"I don't think track and field is dying," US Olympic women's athletics coach Jeanette Bolden said. "Unfortunately it's a situation where something negative happens and that's what people focus on. There have been some negative things.

"But there have been so many exciting things come up. In track and field the best in the sport are coming up at the Olympic trials and you will see that momentum hold to the Olympic Games. You will see the focus go from the negative things to the Olympic team."

Jones was jailed and stripped of her five 2000 Olympic medals, three of them gold, for lying to US investigators about taking performance-enhancing drugs. The BALCO steroid scandal also nabbed Tim Montgomery, her son's father.

Pettigrew joined US Olympic gold medal relay runners Dennis Mitchell and Jerome Young in a doping admission, prompting Michael Johnson to return his medal won with the trio.

Reigning Olympic 100m champion Justin Gatlin is appealing in US courts for a place in Saturday's 100m heats after the Court of Arbitration for Sport ruled against his bid for a reduced doping ban so he might try to race at Beijing.

Denials of wrongdoing and a lack of doping positives by those who later admit wrongdoing have become meaningless and undermined the sport's standard of self-policing, leaving athletes in a no-win situation.

"I think you do feel anger and frustration. Every time you have a good performance, people are questioning you. All you can do is pick up the pace," said Felix, the reigning world 200m champion.

"The system has had problems in the past. I have confidence we're taking steps in the right direction. It's our responsibility to shed some light back on our sport and the best way to do that is with some outstanding performances in Beijing."

Gay and Felix are among the US athletes who volunteered for a US Anti-Doping Agency program, Project Believe, to set body chemistry measures that could better indicate doping when compared to later tests.

"Some people probably are going to say, 'Tyson Gay is on drugs,' and some will say, 'I know he is clean,'" Gay told the Chicago Tribune. "I try not to focus on drug accusations and who is doing what. I just love to compete."

Having seen their idols shamefully return medals won eight years ago, the latest US stars do not want to find glory in Beijing only to suffer the same fate in 2016.

"We're pretty confident with this team that that's a thing of the past generation," Felix said. "We look at our relay teammates and we're pretty confident we're clean. We're making up for other people's past mistakes. That's a common theme running through us."

US Olympic Committee (USOC) and USA Track and Field officials have vowed to send a clean team to Beijing even in the shadow of the historic BALCO scandal.

"We are now looking ahead, focusing on the Team USA squad for the Olympic Games," USA Track and Field president Bill Roe said. "These are the athletes who will take track and field into a brighter present and future."

USOC chief executive Jim Scherr said lessons have been learned.

"The admission by Mr. Pettigrew and other athletes who have admitted to doping during the 2000 Games has only strengthened our resolve to field a clean team in Beijing," Scherr said.

"The only medals we are interested in are those that are won by athletes who compete clean."