DUESSELDORF, Germany -- Andy Roddick and Ryan Harrison lost singles matches Sunday, giving Argentina an unassailable 2-0 lead over the United States on the opening day of the Team World Cup.
The eight-nation tournament on clay is a warm-up for the French Open, which starts in one week.
Roddick, playing his first tournament since March, lost to Carlos Berlocq 6-2, 6-2 in the Red Group. Leonardo Mayer followed by outlasting Harrison 6-4, 5-7, 6-3.
In the Blue Group, defending champion Germany leads Russia 1-0 after Philipp Kohlschreiber defeated Alex Bogomolov Jr. 6-0, 6-2. Serbia took a 1-0 lead over Croatia, with Viktor Troicki beating Ivan Dodig 6-3, 7-6 (3).
Also in the Red Group, Tatsuma Ito put Japan up 1-0 against the Czech Republic by stopping Radek Stepanek 3-6, 6-4, 6-4.