SAINT-DENIS, France -- The United States started slowly at the track and field World Championships, then became mired in controversy. But the Americans flourished Sunday, sweeping three relays to finish first in medals.

The U.S. squad struck gold in the men's 400- and 1,600-meter relays, and a gutsy anchor leg by 18-year-old Sanya Richards gave the Americans a win in the women's 1,600 relay.

Americans took home 20 medals, 10 of them gold, to lead all nations in the nine-day meet. Next was Russia with 19 medals, including six golds. Those numbers could change, based on the resolution of U.S. sprinter Kelli White's drug case.

The U.S. team had averaged 21 medals in the previous eight World Championships, which began in 1983. But this was the first time in a decade the Americans reached 20 medals.

Richards, a sophomore at Texas who became a U.S. citizen last year, held off Russia's Natalya Nazarova and Jamaica's Lorraine Fenton down the stretch to give the U.S. women victory in the 1,600 relay.

"I love running anchor. I always run anchor,'' Richards said. "I'm actually more comfortable running anchor, so I was happy to be there and I was happy to bring it home for the U.S.''

Young, who won the 400 title Tuesday and then became enveloped by a 4-year-old drug case, barely held off France's Marc Raquil to give the U.S. men the 1,600 relay title.

"I just didn't worry about it,'' Young said of the controversy. "I just put it behind me and kept on going, and just basically used that as a motivation.''

Even without 100 world-record holder Tim Montgomery and three-time 100 world champion Maurice Greene, the men's 400 relay team took gold for the third straight World Championships when J.J. Johnson caught Britain's Dwain Chambers in the final few meters.

After a poor baton pass from Bernard Williams to Darvis Patton, Johnson was in third place when he began the anchor leg. First he caught Brazil's Claudio Roberto Souza, then leaned at the finish to edge Chambers and give the Americans the victory in 38.06 seconds.

Montgomery left the meet after a fifth-place finish in the 100, though he had not been expected to run on the relay squad in any case. Greene, who usually runs the anchor leg for the U.S. team, hurt his left leg in the 100 semifinals.

"I felt a lot of pressure because a lot of people thought we couldn't win without Maurice or Tim,'' Williams said. "It shows America is deep, with a good number of sprinters.''

But there were several embarrassments for the Americans in the meet, including the temper tantrum that led to sprinter Jon Drummond's withdrawal and the drug sample that showed White -- who won the 100 and 200, the only U.S. woman to take an individual gold at the meet -- had used a stimulant.

White's case remains under investigation. Though she is likely to lose at least one of her gold medals, world track officials said they need to do more research before deciding on her punishment and passing the case on to U.S. officials.

World track officials said Sunday that White had passed a drug test after her win in the 200. But her positive drug test after the 100 means both medals could be at risk.

USA Track and Field chief executive Craig Masback, making it clear he was not referring to any specific athlete, said positive drug tests are a stain on the image of track and field.

"We as a sport can put on great track meets and get great crowds. A single athlete making one bad choice can create doubt about the sport in some people's minds,'' he said.

The Americans had problems in some events they usually rule, such as medal shutouts in the men's 100 and the women's pole vault. A non-American won the men's shot put for the first time in a decade.

But, after a slow start, the U.S. team rallied with four of the six medals in the women's sprints -- though two could be stripped from White -- and with a 1-2 finish in the men's 200 and a surprise win by Dwight Phillips in the long jump.

"I think that the team has performed quite well, if you look at medal production and clutch performances,'' Masback said.

Also Sunday, Hestrie Cloete of South Africa won her second straight title in the women's high jump, and 18-year-old Eliud Kipchoge of Kenya edged Morocco's Hicham El Guerrouj to win the men's 5,000.

El Guerrouj, who won his fourth world title in the 1,500 on Wednesday, was seeking the first 1,500-5,000 sweep since Finland's Paavo Nurmi won both events at the 1924 Paris Olympics.

Other winners Sunday were Kenya's Catherine Ndereba in the women's marathon, Djabir Said-Guerni of Algeria in the men's 800, Russia's Tatyana Tomashova in the women's 1,500 and Russia's Sergey Makarov in the men's javelin.

For the second straight world meet, there were no world records broken.