CHICAGO (AP) - Paula Radcliffe of Britain needed just two marathons to set a world best for women. As for a third try, she isn't saying.

Running in a biting wind, she completed the Chicago Marathon on Sunday in 2 hours, 17 minutes, 18 seconds. Her time was 89 seconds faster than the mark set by Kenya's Catherine Ndereba in this race a year ago.

Ndereba, the winner in Chicago the previous two years, was the only woman to keep up with Radcliffe until tiring near the end. The Kenyan was a distant second, timed in 2:19.29.

Among the men, Khalid Khannouchi, a U.S. citizen born in Morocco, won in 2:05:56 for his fourth Chicago title. He missed breaking his world best set last April by 18 seconds.

Khannouchi fell to his knees after crossing the finish line, then rolled onto his side and wept.

"This is a magical place to run. That's why I love Chicago. It's just awesome," he said. "The conditions weren't too good and the wind was blowing hard and I just wanted to make sure I won."

Daniel Njenga of Kenya finished second in 2:06:16. Toshinari Takaoka of Japan finished third in an identical time.

Radcliffe refused to say whether her astonishing run was an indication of what's to come or the last time she'll ever race a marathon.

She declined to say if she would enter the Athens Marathon in November or defend her Chicago title next year. In fact, she was noncommittal about any marathons at all.

"I am going to sit down with my (coach and trainer) and see what I think and we'll try and decide what my goals are for next year," she said.

The 28-year-old Radcliffe, an outspoken opponent of performance-enhancing drugs, is a two-time world cross country champion. She faced a frustrating stretch in the 1990s when she faded late in major races. She finished fourth in the 10,000 meters at the Sydney Olympics and fifth in the 5,000 meters at the Atlanta Olympics.

This was the first year Radcliffe had trained for the marathon and it left her in top condition. After running for months in the Pyrenees in France, she won the London Marathon in April in her debut at that distance in 2:18:56.

"Ever since London, I knew I was capable of doing it," Radcliffe said. "This is what I've been working toward."

Chicago was her sixth major win of the year. In addition to London, she defended her world cross country title, won the 5,000 meters in the Commonwealth Games and took first in the 10,000 at the European championships.

Radcliffe was asked what was left for her to accomplish.

"That's a nice dilemma," she said. "It's still really important to me to win the track title in the 10,000 meters. So I've just got to get out there and try and improve at all distances."

On Sunday, Radcliffe was the only runner - man or woman - who didn't tire over the second half of the course. With temperatures in the 30s and the wind gusting up to 15 mph over the final stretch, Radcliffe ran the second half a minute faster than she did the first.

Radcliffe earned $100,000 for first place and another $150,000 for setting the world mark.

She pulled away from Ndereba in the 17th mile. At 5-foot-2 and 98 pounds, Ndereba wilted in the wind off Lake Michigan.

"I was just like, 'Oh, my goodness. I'll be blown away,'" she said.

Yoko Shibui of Japan finished third in 2:21:22, more than two minutes behind Radcliffe.

Radcliffe, who wears a red ribbon when she races in support of compulsory blood testing, insisted her last 10 drug test results be made public after a French magazine hinted she was using performance-enhancing drugs. She authorized release of her blood tests from last year's world half-marathon championship and this year's London Marathon - all of which were clean.

Since 2000, the women's mark has been broken three times and more than three minutes have been taken off the best time.

"I guess there was a mental barrier there," Radcliffe said. "I also think that women are training harder and pushing themselves harder."