Querrey beat Jan Hajek 6-3, 7-5 on Thursday to put the US 1-0 up against the Czech Republic in the Red Group and remain unbeaten in his three singles this week.

The second singles and a doubles will be on Friday. The Americans are bidding to win a fifth title, but a first since 1993.

“So far so good,” said Querrey. “I thought today was the best I played out of the three matches. So I'm pretty excited.” Hajek claimed the first break, when Querrey ended a long rally with a forehand error, to go 3-1 up but the American player responded by winning the next five games in a row to take the opening set.

Both players saved a break point late in the second set before Querrey broke at 6-5, converting his third match point.

“I've been working this week to try and hit my forehand a little bigger. I felt I did that today,” said Querrey. “I felt pretty much anytime I got a forehand, I was able to take control of the point.” Querrey said his win takes the pressure off the US ahead of Friday's matches.

“A little bit, yes. I think John (Isner) can go out there and play a little more freely, which is a good thing,” Querrey said. “When we have the lead, you can swing away a little bit more than if we were 1-0 down.

“Then, the Bryan brothers, we expect them to win every match. Hopefully, they are going to do that again.” The winner of the match between France and Argentina, which stands at 1-1, will qualify from the Blue Group.

Jeremy Chardy put France ahead by beating Juan Monaco 6-3, 6-4 but Eduardo Schwank leveled with a 3-6, 6-3, 6-2 victory over Paul-Henri Mathieu.

In Nice, France, Leonardo Mayer of Argentina rallied to beat fifth-seeded Marcos Baghdatis of Cyprus 5-7, 6-3, 6-4 Thursday and reach the semifinals of the Open de Nice.

The 23-year-old Mayer hit six aces but converted just three of his 24 break points before closing out the match in two hours, 55 minutes.

It was Mayer's first win over a top-30 player since last year's French Open, where he beat American James Blake in the first round.

The 59th-ranked Mayer will now play in his second career semifinal and will meet second-seeded Fernando Verdasco, who struggled to beat Sergiy Stakhovsky of Ukraine 6-2, 6-7 (5), 6-4.

Verdasco won the Barcelona Open on clay earlier this season and is considered a contender to make a deep run at the French Open, which starts on Sunday in Paris.

Verdasco hit seven aces and broke his opponent five times overall. Stakhovsky broke immediately in the third set and went up 3-1 before Verdasco broke back and finished well to seal the match.

“I finished the match playing very well, although I had a problem with my arm,” Verdasco said. “It worries me because I have Roland Garros next week and you don't like to have this kind of problem three or four days before a Grand Slam.”

In Strasbourgh, Vania King of the United States reached the semifinals of the Strasbourg International with a 6-4, 7-5 win Thursday over Anastasia Rodionova of Australia.

King, who upset second-seeded Elena Vesnina in the first round, broke her opponent six times in a match where both players struggled to hold serve. She will next play Kristina Barrois of Germany, who defeated seventh-seeded Anastasija Sevastova of Latvia 6-1, 7-5.

A doubles specialist, King won her only singles title in Bangkok in 2006.