Justin Gatlin insisted on running at the national championships in June even after USA Track & Field officials asked him to withdraw over his positive drug test, a person with knowledge of the meeting told the Associated Press on Friday.
Because only the "A" sample result was available from the April test at the Kansas Relays, USATF had no authority to bar Gatlin from competing.
Results of the backup "B" sample are required before a doping test is considered positive.
Gatlin professed his innocence to USA Track & Field officials when they suggested that he drop out of the meet, said the source, who asked not to be identified because of the sensitive nature of the information.
The 100 meters co-world record holder went on to win the national 100-meter title and was mobbed by fans afterward. Gatlin, who tied Jamaican Asafa Powell's world-record mark of 9.77 seconds three weeks after his fateful drug test, has not raced since.
He canceled several European appearances, citing a leg injury.
Gatlin's agent Renaldo Nehemiah and his attorney Cameron Myler did not return telephone messages Friday. Gatlin and USATF learned of the positive test just days before the U.S. championships began June 21 in Indianapolis.
By then, it was too late remove Gatlin's photograph from the meet's posters and the many banners hung around the city.
The 24-year-old sprinter showed up at the pre-meet news conference offering no hint of what was hanging over him.
"I'm going to strive for my goals, and I'm going to go out there and make sure I put the world record out of reach by the time I retire," he told reporters.
Craig Masback, executive director of USA Track & Field, said he was shocked when he first learned Gatlin had tested positive after the relay race in Kansas in April.
"It's a grave situation," Masback said Friday in a telephone interview from Europe.
"It's a positive lab test for an athlete that has spoken clearly on the need to compete with integrity and without drugs."
Gatlin, Masback acknowledged, had been the "standard bearer" for the anti-doping cause among U.S. athletes.
In early June, on the eve of the Prefontaine Classic in Eugene, Ore., Gatlin welcomed the role of leader of a young, talented group of U.S. track athletes.
"We have a lot of young athletes - Jeremy Wariner, Sanya Richards, Allyson Felix - who are running world-class times, proving to the world there's no need for those cloudy allegations anymore," he said at the time. "We're trying to bring the sunshine back to track and field."
Gatlin also acknowledged he always would draw suspicion because his coach is Trevor Graham - who has had numerous athletes suspended for doping - and because he was suspended as a young college sprinter for using a prescribed medicine to treat attention deficit disorder.
"It's something I've grown to live with, something that keeps me fighting as an athlete, helping other sprinters and other youth come along and try to steer track and field in the right direction," Gatlin said.