Tyson Gay won’t get the chance to face off with Usain Bolt in the 100- and 200-meter sprints at next month’s world championships. (Andy Lyons/Getty Images)

American sprinter Tyson Gay, who posted some of the fastest times of his career in preparation for next month’s track and field world championships in Moscow, disclosed Sunday he had tested positive for a banned substance.

As a result, Gay, 30, will withdraw from worlds, scuttling his highly anticipated clash with Usain Bolt in the 100- and 200-meter sprints, and travel to Colorado Springs, where officials with the U.S. Anti-Doping Agency are expected to report early next week whether his “B” sample confirms the failed, out-of-season test conducted May 16.

Gay revealed his positive test in a telephone interview with the Associated Press, reportedly fighting back sobs as he spoke.

“I don’t have a sabotage story,” Gay told the AP from his training base in Amsterdam. “I don’t have any lies. I don’t have anything to say to make this seem like it was a mistake or it was on USADA’s hands, someone playing games. I don’t have any of those stories. I basically put my trust in someone, and I was let down.”

Neither Gay nor officials from USADA, USA Track & Field or the U.S. Olympic Committee would disclose the substance for which he tested positive. But unless the B-sample exonerates him, which is unlikely according to those familiar with the testing protocol for the substance, he could be suspended from competition for six months or longer.

A world champion in the 100, 200 and 4x100-meter relay in 2007, Gay battled hamstring and groin injuries over the last five years. As a result, he failed to win a medal at the 2008 Beijing Olympics. He set the U.S. mark in the 100 at 9.69 in 2009. After undergoing hip surgery in 2011, he finished a heartrending fourth in the 100 at the 2012 London Games, just .01 of a second out of a bronze medal.

But this season, he has enjoyed a resurgence. In a three-day span in June, he ran the fastest time of the year to win the 100 (9.75 seconds) and 200 (19.74 seconds) at the U.S. championships in Des Moines, which set up the showdown with Bolt at worlds.

A self-described “country boy” from Lexington, Ky., Gay, who competed in college at Arkansas, is widely regarded as humble and grounded, in contrast to many world-class sprinters.

As part of USADA’s “My Victory” program, Gay is among 11 U.S. Olympians who volunteered for extra-rigorous drug testing to show support for drug-free competition. His online testimonial read: “I compete clean because I really believe in fairness. And besides that, my Mom would kill me!”

As news of the positive test leaked Saturday and was confirmed by the sprinter Sunday, it was met with surprise and empathy by many in the sport.

“It is not the news anyone wanted to hear, at any time, about any athlete,” Max Siegel, chief executive of USATF, said in a statement expressing support for USADA’s adjudication process.

USADA commended Gay’s candor and cautioned against a rush to judgment.

“USADA appreciates his approach to handling the situation and his choice to voluntarily remove himself from competition while the full facts surrounding his test are evaluated,” its statement read. “As in all cases, all athletes are innocent unless or until proven otherwise through the established legal process, and any attempt to sensationalize or speculate is a disservice to due process, fair play and to those who love clean sport.”

Said Patrick Sandusky, chief communications officer for the USOC: “We are aware of the test and, as in all cases, will allow due process to run its course. Until then, we will refrain from commenting.”

In disclosing the positive result, Gay joined a trend of world-champion athletes attempting to “get out ahead” of negative publicity about otherwise unsullied careers. He was followed within hours by Jamaican sprinters Asafa Powell and Sherone Simpson, whose agent told the AP on Sunday they had each tested positive for the banned stimulant oxilofrine.