Hoffman Estates - Sam Querrey gave the U.S. a commanding 2-0 lead Friday night in its Davis Cup World Group playoff against Slovakia with a 7-6 (6), 6-3, 6-3 win over Martin Klizan.
In the opening match of the night, American John Isner hit 29 aces in a 7-6 (5), 6-4, 6-2 win over Norbert Gombos.
The U.S. can ensure a trip to the 2015 World Group on Saturday by winning the doubles when it sends out U.S. Open champs Mike and Bob Bryan.
Querrey, ranked 51st, faced a set point in the first-set tiebreaker at 5-6, but responded with two straight aces. He captured the opening set when the 57th-ranked Klizan netted a backhand. Querrey finished with 20 aces on the hard court at the Sears Centre.
Gombos, ranked 126th, was a surprise choice as Slovakia's No. 2, but he showed his skills during a group quarterfinal in April when he made his Davis Cup debut and beat Austria's Dominic Thiem.
But this time he had to fight off the powerful serves of Isner and managed only two breakpoint opportunities.
"Going into a match like this, three-out-of-five match, it's not surprising I didn't lose my serve," Isner said. "I've done that before, for sure. Always going to be the biggest part of my game and it's going to be the part of my game that I lean on the most."
Isner trailed in the first-set tiebreaker 4-2 before pulling it out 7-5 when Gombos netted a volley and hit long after a strong serve.
Isner then broke Gombos in the opening game of the second set and his game improved steadily thereafter.
"I was a bit nervous in the beginning. I had to really dig deep to win that first set. But once I got that under my belt, I exhaled and then I started to play better," Isner said. "It's never easy. But that first set was very important."
Serving for the second set at 5-4, Isner double faulted twice but then won the next four points with an ace, a volley, an overhead and a service winner.
"I know that he's serving perfect, like from the Eiffel Tower, you know," Gombos said. "I never returned a serve like his because it's quite different from the other players because he is really tall. The ball is bouncing so high."
Isner said he was aware of how well Gombos, who has flat groundstrokes and good speed around the court, can play.
"It's a tough match for someone like me," Isner said. "We're at home. I'm ranked higher than him. I guess on paper I'm expected to win that match. There's a lot of pressure on me. It's not an easy situation."
The U.S., which lost to Great Britain earlier this year, hasn't missed competing in the World Group, the upper tier, since 1988.
Slovakia is trying to pull the upset and make it back to the World Group for the first time since 2006.