Serena and Venus Williams, the world's top two ranked women's players, were named in the United States Fed Cup team on Sunday.

The United States will face the Czech Republic in the first round from April 26-27 in Lowell, Mass. in a best-of-five match series.

U.S. Fed Cup captain Billie Jean King has until April 16 to nominate the remainder of the U.S. team.

The inclusion of the Williams sisters marks the fifth time that the top two ranked players will compete on the same team.

"We have the great fortune of having the best two players in the world with Serena and Venus," King said in a statement. I look forward to assembling the rest of the team and bringing the greatest players the U.S., and the world, have to offer to Lowell, Mass."

"I'm looking forward to representing my country and am excited to be part of the Fed Cup team again," said Serena. "I've always had a great time playing Fed Cup and enjoy being together with the other U.S. players."

Venus added: "Having the opportunity to represent your country is such an honour.

"I'm looking forward to some great competition and hope to bring home a victory for the U.S."

Last month Serena became the fifth woman to win hold all four grand slam titles at the same time following her triumph at the Australian Open.

The 21-year-old, 3-0 in Fed Cup play, won the U.S. Open, Wimbledon and French Open crowns in 2002 and has also captured eight grand slam doubles titles.

Four-times slam winner Venus is 5-1 lifetime in Fed Cup play.

The U.S. defeated the Czech Republic 3-0 in their only previous meeting in 1994.