World number one Serena Williams and her sister Venus will join Sloane Stephens and Varvara Lepchenko on the US Fed Cup team facing Sweden later this month, the US Tennis Association said Wednesday.
The move ensures the Williams sisters, two-time defending Olympic women's doubles champions as well as the 2000 Sydney Olympic winners, will be eligible to play in the 2016 Rio de Janeiro Olympics.
Serena Williams, a 15-time Grand Slam singles champion, is also the reigning Olympic singles champion.
The Americans, all ranked in the WTA top 30, will play host to Sweden at Delray Beach, Florida, on April 20-21, with the winner qualifying for the 2014 World Group and the loser relegated with no chance to win the trophy next year.
"I'm really excited about the team that we have," US Fed Cup captain Mary Joe Fernandez said. "We have great talent and depth, which is a perfect combination."
Venus Williams is ranked 22nd, six spots behind Australian Open semi-finalist Stephens and five ahead of Lepchenko.
Sweden's team features 54th-ranked Sofia Arvidsson, 65th-ranked Johanna Larsson, 425th-ranked Hilda Melander and 489th-ranked Sandra Roma.