DELRAY BEACH, Fla. (AP) _ With Serena Williams sidelined, Fed Cup teammate Vania King showed she can do more than sing.
The 18-year-old King won raves for her rendition of the national anthem to start the weekend, then substituted Sunday for Williams and sealed the U.S. team's victory over Belgium.
King beat Kirsten Flipkens 4-6, 6-4, 7-5, giving the Americans an insurmountable 3-0 lead en route to a 5-0 victory. They'll face Russia in the semifinals after Wimbledon.
Serena and Venus Williams won in singles Saturday, then became cheerleaders rooting from the bench for King.
``It's a great feeling, because they're champions I really look up to,'' King said. ``It's really honoring.''
``She had a great performance,'' Serena Williams said. ``It was a pressure match, because it was the clincher. She was down a lot, but she was able to come back. I thought it was a great match.''
Williams pulled out a few hours before she was to face Flipkens, citing soreness in her right knee diagnosed as slight inflammation. She said the knee started bothering her before Saturday's match, but she didn't think it would hamper her preparation for the French Open next month.
Williams said the ailment was unrelated to the groin injury that forced her to retire from a match in Charleston, S.C., on April 10.
After King won, Venus Williams beat Yanina Wickmayer 6-1, 6-2. In doubles, King and Lisa Raymond beat Tamaryn Hendler and Caroline Maes 6-1, 6-2. The Belgians were without their best players, top-ranked Justine Henin and No. 4 Kim Clijsters, who decided to take the week off.
The Americans will play Russia on July 14-15 at a U.S. site to be announced. Russia advanced by beating Spain 5-0.
Venus Williams said she plans to play against the Russians, but her sister was noncommittal.
``We'll see,'' Serena said. ``It's a long season. It's right after Wimbledon. I think there's a good possibility.''
France and Italy also won 5-0 and will meet in the other semifinal.
King is a trained soprano and also the lone teenage American woman ranked in the top 100. But she's only 4-8 this year and said she began the match more nervous than when she sang the day before.
``It's a different feeling playing for yourself and playing for your country,'' the Californian said. ``I felt like it's my responsibility to do the best I can for my country. It's not just about me anymore.''
She was fitter at the finish against Flipkens, who battled leg cramps and repeatedly required massages during changeovers in the final set.
Flipkens was also unlucky: A disputed line call went against her when she was serving for the match at 5-4, and on the next point she lost the game. Flipkens said she received several messages from supporters after the match saying the ruling was wrong.
``That's life. That's tennis. People make mistakes,'' the Belgian said. ``That one point didn't make the match.''
In the final game a gimpy Flipkens double-faulted and committed three unforced errors, and King whacked a forehand passing shot for a winner on the second match point.
That earned the teen a hug from U.S. captain Zina Garrison, and the team began a flag-waving celebration.
``I felt like after the first set I loosened up a little bit,'' King said. ``The whole team was there behind me and cheering me on, and Zina was always pumping me up, trying to keep me positive and fighting hard. So thanks to them.''
The match was entertaining but sloppy, with the timing of both players thrown off by wind so strong it blew a ball can past the baseline. They waged long rallies that occasionally evolved into an exchange of moonballs, but both also came to the net for frantic exchanges.
After her slow start, King won the final four points of the second set to pull even, and she went on to her first Fed Cup victory.
When asked if King's stock had risen, Garrison smiled.
``Vania's stock rose yesterday when she sang the national anthem,'' Garrison said.
In Moscow, Svetlana Kuznetsova clinched Russia's victory by beating Anabel Medina Garrigues 6-3, 4-6, 6-0. Russia is seeking its third Fed Cup title in four years, while the Americans are bidding for their 18th Fed Cup title. They've won the event more than any other country.
In Castellaneta Marina, Italy, Tathiana Garbin rallied past Zhang Shuai 3-6, 6-2, 6-4 to clinch the Italians' victory over China. Italy is the defending champion.
In Limoges, France, Tatiana Golovin beat Ai Sugiyama 7-6 (3), 6-0 to seal France's win over Japan.