Olympic champion Dayron Robles was disqualified for interfering with Chinese star Liu Xiang in the 110-meter hurdles Monday, giving runner-up Jason Richardson of the United States the victory in one of the most anticipated races at the world championships.

In a race almost as controversial as the 100 final disqualification of Usain Bolt a day earlier, Robles crossed the line first, but Liu appealed after the Cuban tangled with him over the two last hurdles, which dropped Liu into third place.

The track referee disqualified Robles for "obstruction."

An appeal by the Cubans was denied. The American benefited when Liu slowed down after contact was made with Robles, and finished second.

"When I approached the ninth hurdle, Robles pulled me. It made me slow down," said Liu, who was moved up to second. "At first, I thought I would be the champion or at least second. But Robles pulled me."

Liu said he did not believe the interference was intentional in a race known for flying arms and legs in close quarters.

"I am really sorry about the situation. You know competition," Liu said. "Besides, we are good friends."

Instead, it was Richardson who ran away with this year's biggest prize.

"Whatever reward I get from doing my best, I will accept. If it's gold, silver or bronze, it doesn't matter," Richardson said. "It's bittersweet. You never want to see someone as talented as Robles disqualified."

The decision left the Cubans angry.

"He won the race. That's what we know," said Robles' coach, Santiago Antunez.

Liu was adamant there was interference between the runners in the neighboring lanes.

With David Oliver, Robles and Liu, the three fastest men in history lining up against each other, an exciting race was assured.

Oliver was the first man out, but plowed into the second hurdle and never recovered. Robles had used his quick start to build a sizable lead, but Liu nearly caught him with two of the 10 hurdles remaining.

Robles and Liu first seemed to touch when clearing the ninth hurdle, and then again on the final one. Liu caught the final hurdle between his legs and lost vital momentum as he fell back.

Oliver, a pre-race favorite from the U.S. who ended up fourth, said such tangles in an action-packed race should be no reason to change the result.

"So he might have gotten dq for hitting Liu, man that happens almost every single hurdle race, happened to me in the semi...tough break," Oliver wrote on Twitter.

Robles finished in 13.14 seconds, followed by Richardson in 13.16 and Liu in 13.27. Turner finished in 13.44, the same official time as Oliver.

The Americans won a sprint title for sure when Carmelita Jeter rallied to take the 100 over Jamaican veteran Veronica Campbell-Brown. Kelly-Ann Baptiste of Trinidad and Tobago took bronze.

The U.S. was expected to top the women's 400, but it was Amantle Montsho who gave Botswana its first medal at a world championship by taking the gold.

Allyson Felix, a three-time world champion in the 200, was even with Montsho as they entered the final straight but couldn't overtake her in the stretch. Felix was looking for a 200-400 double at the worlds and two relay titles as well.

Montsho won in a national record time of 49.56. Felix was second in 49.59 and Anastasiya Kapachinskaya of Russia was third in 50.24.

Defending champion Sanya Richards-Ross of the U.S. finished seventh in 51.32.

Also, Pawel Wojciechowski of Poland won gold the pole vault, clearing 19 feet, 4 1/4 inches. He beat Lazaro Borges of Cuba, who cleared the same height, because of fewer misses. Favorite Renaud Lavillenie of France took the bronze.

Koji Murofushi of Japan won the hammer throw, edging Krisztian Pars of Hungary. Murofushi twice threw 266 feet, 6 inches to win gold, holding off Pars by two inches. Primoz Kozmus of Slovenia took the bronze at 260-5.

Murofushi, the 2004 Olympic champion, won his first world title at 36.

In the women's shot put, Valerie Adams of New Zealand defended her title, winning with a throw of 69-8 1/4. Nadzeya Ostapchuk of Belarus was second with 65-9 1/2 and Jillian Camarena-Williams of the U.S. took third with 65-8 1/4.