BERLIN, Aug. 15 (Xinhua) -- Olympic champion Valeriy Borchin of Russia won the first gold of the world championships in the men's 20km walk while Kenya's Linet Masai broke Enthiopia's 10-year dominance in the women's 10,000 meters with a thrilling win here on Saturday.

    Usain Bolt and Tyson Gay both cruised into the semifinals of the 100 meters, setting up the prospect of a showdown in Sunday's final.

    Bolt, the three-time Olympic champion from Jamaica, and Gay, the three-time world champion from the United States, proved they are in form for the most anticipated race of the year.

    Gay won his quarterfinal in 9.98 seconds, and Bolt advanced in at 10.03, finishing second in his heat.

    "I was happy, I didn't need to do any more work," Bolt said after his qualification.

    Borchin, 23, who won his first major title in Beijing in commanding fashion, lived up to expectations by taking control after 15 kilometers. China's Wang Hao, who missed a medal in the Beijing Olympic by just five seconds, took the silver and Mexico's Eder Sanchez finished third.

    Kenya's Linet Masai broke the Ethiopia's 10-year dominance to win the women's 10,000m title.

    The 19-year-old Masai overtook Ethiopia's Meselech Melkamu in the final moment. Melkamu raised her hands and slowed down before crossing the finish line and celebrated too early.

    Masai, fourth in the Beijng Olympics, caught Melkamu and women's 5,000m Olympic champion Meseret Defar on the line in a thrilling final with two meters to go.

    "I can't believe it! I'm so grateful for the win. I didn't give up," Masai said.

    Melkamu won the silver and her compatriot Wude Ayalew was third. Defar had to be satisfied with fifth.

    "I'm very disappointed that we lost the gold," said Melkamu. "I would have been happy if Meseret had got the gold. I was expecting her to win. I never saw the Kenyan."

    Olympic and two-time defending world champion Tirunesh Dibaba of Ethiopia did not compete because of injury.

    The men's shot put gold was won by Christian Cantwell of the United States, who avenged his Beijing defeat by beating Olympic champion Thomasz Mazewski of Poland.

    Ralf Bartels earned the first medal for host nation Germany with the bronze.