Chicago:Hrachik Javakhyan of Armenia outmaneuvered lightweight Sadam Ali to eliminated the American from the World Boxing Championships on Sunday.
Javakhyan outscored Ali early, then protected his lead by moving around the ring and effectively countering Ali's attacks.
Ali successfully adjusted his style to keep the match close, but Javakhyan managed the fight well and won by a score of 20-16.
"It just wasn't my day," said a disappointed Ali, who will have two more chances to qualify for the Olympics at upcoming tournaments in Guatemala and Trinidad and Tobago.
Earlier in the day, China's top-ranked light flyweight Zou Shiming continued his dominance in the ring with a 30-13 victory over Kazakhstan's Birzham Zhakypov.
Russian Alexey Tishchenko, a gold medalist in the Athens Olympics and one of the best pound-for-pound amateur boxers in the world, defeated Joung-Won Kim of Korea 27-20.
"It was a little bit more difficult than I expected," Tishchenko said through a translator following the match, adding that he still expects to win in his weight class.
High school student Luis Yanez and welterweight Demetrius Andrade, both of the United States, won their bouts to advance. Yanez won by walkover, while Andrade beat Latvia's Dmitrijs Sostaks 19-3.
The top eight finishers in the light flyweight (48kg) to light heavyweight (81kg) divisions, and the top four from the heavyweight and super heavyweight classes qualify for the Beijing Olympics.
Chicago was elected to host the World Boxing Championships after Moscow lost the event earlier this year.