LOWELL, Mass. -- Venus and Serena Williams will work double-duty for the United States in the first-round of the Fed Cup against the Czech Republic.

Venus Williams will play the opening match on Saturday against Daja Bedanova, followed by Serena Williams against Iveta Benesova. On Sunday, they'll switch opponents and play another pair of singles matches.

The Williams sisters also are scheduled to play doubles against Eva Birnerova and Klara Koukalova. Doubles players can be changed up to 15 minutes before the match.

Serena Williams is the top-ranked women's player in the world, and her older sister is No. 3. The U.S. squad also includes No. 19 Meghann Shaughnessy and No. 26 Alexandra Stevenson.

Bedanova is the top player on the Czech team, at No. 44.

U.S. captain Billie Jean King said she was not worried that her players would be overconfident when they play at the Tsongas Arena.

"The better you get, the more you understand that you can never take anything for granted,'' she said Friday. "To keep themselves at such a high level, all these players know that they have to keep working hard. Overconfidence isn't something we have to worry about.''

Czech captain Petra Langrova-Pichalova said that being an overwhelming underdog takes all the pressure off her team.

"The U.S. team is very strong,'' she said. "I just tell the girls we have nothing to lose. The girls can feel free and try to play the best tennis they can.''

Slovakia defeated Spain to win the Fed Cup last year. But with the Williams sisters playing, the Americans are favored to capture the 16-team event for their 18th Fed Cup.

Serena and Venus played on the 1999 Fed Cup team that won the title over Russia. Serena is 3-0 in the Fed Cup, while Venus is 5-1.

"When you get in this competition, you get more motivation because it's not just you, you're playing for the whole team,'' Venus Williams said. "So that's what I have to be ready for.''

Belgium, the 2001 Fed Cup winner, opens at home against Austria. The Belgians are strong with No. 2 Kim Clijsters and No. 4 Justine Henin-Hardenne.

In other matches, it's Slovakia-Germany, Argentina-Slovenia, Sweden-Italy, Russia-Croatia, Spain-Australia and Colombia-France.