-- China enjoyed two sweet surprises on the Olympic Stadium track Friday, one unfolding in fewer than 13 seconds and another in half an hour. Two youngsters likely to be full-fledged stars by the 2008 Summer Games got the world's attention with gold medal performances.

Liu Xiang, 21, won the Olympic gold medal in the 110-meter hurdles, matching an 11-year-old world record in the process. Later in the evening, Xing Huina, 20, set a personal best in winning the women's 10,000 meters a year after having broken the world junior record in the event.

"I think today the Chinese people showed the world they can run as fast as anybody else," Liu said. "I'm so happy I don't even have the power to cry."

Liu's performance bordered on stunning. Barely clearing each hurdle, he surged across the finish in a time of 12.91 seconds, equaling the world record set by Britain's Colin Jackson and topping the Olympic record of 12.96 set in 1996 by District native Allen Johnson. American Terrence Trammell claimed the silver in a distant 13.18, followed by Cuba's Anier Garcia, who tumbled across the line in 13.20.

Two years ago, Liu had asked for Johnson's autograph at a meet. This week, he declared Johnson -- who had crashed, failing to advance to the final -- his idol. Friday, he became Olympic champion.

"This feels like kind of a miracle," he said. "I didn't dare to think I would get a medal of any kind here."

Xing, meantime, caught the entire field by surprise. She finished in 30 minutes 24.36 seconds, just .62 of a second ahead of Ethiopian Ejegayehu Dibaba, who claimed not to have seen Xing as she raced to the finish in a spread-out field.

"I thought I'd won," said Dibaba, who ran a personal best. "I'm really surprised that I don't have the gold medal. I missed the Chinese athlete completely. Had I seen her, I would have put in more effort and passed her."

Said bronze medal winner Derartu Tulu of Ethiopia, who finished in 30:26.42: "We were not afraid of the others. We just didn't pay attention to the Chinese. I am disappointed."

Xing reveled in her achievement, even if others considered it tarnished. A Chinese junior champion in the 1,500, 5,000 and 10,000, she finished seventh in the 10,000 at last year's world championships in Paris.

"Winning the championship was beyond expectation," she said. "I am so happy about it. I think our efforts deserve a reward."

Radcliffe Bows Out

For the second time in less than a week, Britain distance star Paula Radcliffe finished a race in tears. Radcliffe, who bowed out of the Olympic marathon with just a few miles remaining, walked off the track in the 10,000 Friday with about eight laps left because of leg pain.

"I just seized up," she said. "On Sunday, I had to stop in the marathon because of sheer exhaustion. Today, it wasn't exhaustion but my leg that forced me out of this race. It was just too sore . . . I went out there and gave it a shot, but it just wasn't there." . . .

American Tim Mack set an Olympic record in the pole vault and sealed the gold medal when he vaulted to 19 feet 61/4 inches on his final attempt.

Mack made three final attempts at 19-81/4, but failed to get over the six-meter mark, significant in Europe. The only Americans to clear that height are Toby Stevenson, who jumped 19-41/4 for the silver Friday, and Jeff Hartwig, the American record holder who no-heighted at the U.S. Olympic trials.

Relay Teams Advance Easily

The United States easily advanced in the first rounds of the men's 4x100 relay and the men's 4x400. A team that included Olympic 200 champion Shawn Crawford, Darvis Patton, Coby Miller and 100 bronze medallist Maurice Greene finished in 38.02 seconds, .25 ahead of Nigeria. Greene said the United States would break its own world record of 37.40 in Saturday's final round. "I'm predicting a time of 37.27," he said.

In the 4x400, Kelly Willie, Derrick Brew, Andrew Rock and Darold Williamson finished first in 2:59.30, topping Nigeria (3:01.60).

The U.S. women's 4x400 relay team, hampered by a slow opening leg by Crystal Cox, finished second to Russia in Friday's semifinals. Russia crossed the line in 3:23.52; the U.S. team of Cox, Moushaumi Robinson, Monique Henderson and Sanya Richards finished in 3:23.79.