BUENOS AIRES, Argentina (AP) -- Venus Williams opens against Paula Ormaechea on Saturday when the United States takes on Argentina in World Group II of the Fed Cup.

The United States is an overwhelming favorite to win the tie with sister Serena Williams in second singles on Saturday against Maria Irigoyen. The best-of-five series on clay finishes Sunday.

Friday's draw was a reminder of the likely mismatch. The Williams sisters have won 56 different Grand Slam singles, doubles and mixed doubles titles. Serena is fresh from winning the Australian Open singles title.

Ormaechea is ranked No. 121 by the WTA and Irigoyen is No. 197.

The winner advances to the World Group playoffs April 18-19 with a chance for a spot in the 2016 World Group—the top grouping in the team competition.