The U.S. team opened the tournament with a 3-0 win over Czech Republic, and followed it up with a victory over another opening-day winner.
Vandeweghe beat Lara Arruabarrena 6-2, 6-4 and Sock had a 3-6, 6-2, 6-3 win over Feliciano Lopez in the singles matches before teaming up to win the mixed doubles 4-3 (3), 3-4 (2), 4-3 (2).
Defending champion Australia was to play the Czech Republic in a night match, needing a win to stay in contention following an opening 2-1 loss to Spain.
Original author: Ashley Ndebele