LONDON — The U.S. had a big lead when Carmelita Jeter got the baton for the anchor leg of the women’s 4x100-meter relay on Friday night.

She knew exactly what to do with it.

Jeter powered down the stretch and pointed the baton at the clock as she crossed the finish line, celebrating a world-record time of 40.82 seconds that gave the Americans their first victory in the event since 1996.

Tianna Madison, 200-meter champion Allyson Felix, Bianca Knight and Jeter combined for a perfect trip around the track that ended a string of disappointments for the U.S. in the marquee relay. At the 2008 Beijing Games, the Americans didn’t even reach the final because Torri Edwards and Lauryn Williams bobbled the last exchange in the semifinals.

Their final time cut more than a half-second off the old record of 41.37 run by East Germany in 1985.

“I just knew if we had clean baton passes that we would definitely challenge the world record,” Madison said. “Smash it like we did? We had no idea, but I knew it was in us.”

Jamaica won the silver medal in a national record of 41.41 seconds, with 100 champion Shelly-Ann Fraser-Pryce, Sherone Simpson, Veronica Campbell-Brown and Kerron Stewart bringing the baton around.

Kevin Durant and the U.S. men’s basketball team also had quite the closing kick in their semifinal against Argentina.

Durant scored 19 points and LeBron James did a little bit of everything as Team USA pulled away for a 109-83 victory and a spot in Sunday’s final against Spain.

Argentina trailed by four early in the second half when the United States put the game away behind the strength of James and Durant’s shooting ability.

Durant made two 3-pointers in an 8-0 spurt that pushed the lead to 13, and when Argentina got back within eight, the NBA’s MVP and runner-up teamed up to blow it open.

James had a basket and drove for a powerful dunk while being fouled. Durant followed with consecutive 3-pointers, and James tipped in a miss and suddenly the lead was 19, 72-53, with 1:30 left in the period.

Back on the track, the American team was in control in the men’s 4x400 relay until Ramon Miller of the Bahamas chased down Angelo Taylor on the anchor leg to grab his country’s first gold in a race won by the U.S. in every Olympics since 1984.

But the silver helped the United States run its lead in the medals table to 94-81 over China.

The South African team, anchored by double-amputee “Blade Runner” Oscar Pistorius, fell behind well before Pistorius received the baton and was eighth.

Turkey’s Alsi Cakir Alptekin (women’s 1,500 meters), Ethiopia’s Meseret Defar (women’s 5,000 meters) Russia’s Tatyana Lysenko (women’s hammer throw) and France’s Renaud Lavillenie (men’s pole vault) were the other winners at Olympic Stadium.

European champion Alptekin, who served a two-year suspension for doping after the 2004 world junior championships, led a 1-2 finish for Turkey in her race. She finished in 4:10.23 and Gamze Bulut was next in 4:10.40.