Defending light flyweight champion Zou Shiming, a bronze medalist at the Athens Olympics, routed David Ayrapetyan of Russia 23-6 on Wednesday to reach the quarter-finals of the World Boxing Championships.
By making the last eight, the Chinese earned a spot in the Beijing Olympics in his home country.
It marked Russia's first loss at the championships that started more than a week ago. Russia entered competition on Wednesday with a 22-0 record.
"He was good, outstanding. I was better," Zou said through a translator.
Russia's Alexey Tishchenko, the reigning Olympic featherweight champ, rolled to a lightweight victory over Husnu Kocabas of the Netherlands and will go after another gold medal in Beijing.
With Tishchenko ahead 25-5, the lopsided contest was stopped by referee Rogello Fortaleza in the third round. Tishchenko will meet Pichai Sayota of Thailand, who advanced with a 21-13 victory over Mongolia's Uranchimeg Munkh-Erdene.
Two Americans also advanced to the quarter-finals: light flyweight Luis Yanez beat Stephen Sutherland of Australia with the referee stopping the contest in the second round while Rau'shee Warren beat Violito Payla of the Philippines 25-11 in the flyweight division.
The top eight finishers in the light flyweight to light heavyweight divisions and the top four from the heavyweight and super heavyweight classes qualify for the Olympics. There also will be two continental qualifiers early next year, so this is not the last chance to make the Olympics.
Earlier, officials announced that heavyweight Ihab Al Matbouli of Jordan, who collapsed in the ring from fatigue during one of the final bouts Tuesday night, had rejoined his team after all tests taken at a Chicago hospital were negative.