Melanie Oudin and Bethanie Mattek-Sands of the United States lost their singles matches Saturday, giving Belgium a 2-0 lead in the first-round Fed Cup matchup.

Oudin lost to Australian Open winner Kim Clijsters 6-0, 6-4, and Mattek-Sands fell 6-1, 7-6 (6) to Yanina Wickmayer in the opening match.

The United States played without the injured Williams sisters. Venus Williams strained her groin at the Australian Open, and Serena Williams has been sidelined with a foot injury since winning Wimbledon.

Belgium competed without Justine Henin, who retired last week because of an elbow injury.

In other Fed Cup matches, defending champion Italy and Australia tied 1-1. Flavia Pennetta edged Samantha Stosur 7-6 (5), 6-7 (5), 6-4, and Jarmila Groth upset French Open champion Francesca Schiavone 6-7 (4), 6-3, 6-3.

France leads Russia 2-0 after Maria Sharapova and Svetlana Kuznetsova lost their matches. Virginie Razzano defeated Sharapova 6-3, 6-4 after Alize Cornet rallied to beat Kuznetsova 3-6, 6-3, 6-4.

The Czech Republic has a 2-0 lead over Slovakia. Lucie Safarova beat Daniela Hantuchova 7-5, 6-1, and Petra Kvitova stopped Dominika Cibulkova 6-2, 6-3.

Clijsters is the favorite to clinch the event Sunday when she plays Mattek-Sands in reverse singles.

"Everybody always expects a lot, but it isn't always that easy," said the second-ranked Clijsters.

Clijsters cruised in the first set against the 61st-ranked Oudin. The 19-year-old from Marietta, Ga., put up a better challenge in the second set.

"It kind of got in my head, and I was just tight out there in the beginning," Oudin said.

Clijsters finished the match with an ace to the cheers of the crowd of 10,000 at the Sports Palace.

Mattek-Sands littered the first set with unforced errors but fought for every point in the second to force a tiebreaker, losing the match when the ball bounced unluckily on the net cord in the tiebreaker.

Mattek-Sands had forced two set points and took a 5-2 lead in the second-set tiebreaker before the Belgian rallied.

"It is good to have the first point under the belt," Wickmayer said. "It certainly wasn't easy."

Henin's retirement gave the starting spot to Wickmayer, who was still shaking off a bad cold.

Mattek-Sands sprayed balls all over, helping Wickmayer to a 3-0 lead. She never recovered in the first set and seemed finished after Wickmayer immediately broke in the second. But Mattek-Sands, ranked 48th compared to 26th for Wickmayer, fought back.

"She is a great Fed Cup player," Wickmayer said.

Mattek-Sands next faces Clijsters, who owns four Grand Slam singles titles.

"There is no use worrying about what's in the past," she said. "Go out there and play my game, that's all I can control."