Serena Williams rallied from a set down to beat Anastasia Yakimova 5-7, 6-1, 6-1 on Sunday and clinch the United States' victory over Belarus in a Fed Cup World Group-II tie.
Williams, a 13-time Grand Slam champion, claimed her second singles win of the weekend after beating Olga Govortsova on Saturday in Worcester, Massachusetts.
Yakimova was a late replacement in singles for Australian Open champion Victoria Azarenka, whose triumph in Melbourne saw her claim the women's world number one ranking.
Azarenka had been expected to lead Belarus but pulled out with a sore lower back. She said travel from Australia had exacerbated the problem.
Williams' victory over Yakimova gave the Americans an unassailable 3-0 lead in the best-of-five match tie. Christina McHale beat Yakimova on Saturday for the Americans' first point.
The winners advance to the World Group Playoff and play for a chance to return to the elite group in 2013.
The United States have won the women's nations competition a record 17-times and are playing in the World Group-II for the first time.
Belarus have never played in the World Group.