Serena Williams is on the U.S. Fed Cup roster for matches against Ukraine on April 21-22, but her sister Venus is not.
Joining the 13-time Grand Slam champion on the team announced by Fed Cup captain Mary Joe Fernandez on Wednesday are Christina McHale, Sloane Stephens, and Liezel Huber.
The best-of-five-match series will be on clay at Kharkiv, Ukraine.
The country that wins will be promoted into the main Fed Cup group in 2013 and be able to compete for the title. The loser will drop into World Group II.
Serena Williams is making her second consecutive Fed Cup appearance after winning twice against Belarus in February to improve to 6-0 in singles play in the team competition.