Houston - Top-seeded John Isner of the United States beat South Korea's Chung Hyeon 7-6 (5), 6-4 on Friday night in the U.S. Men's Clay Court Championship quarter-finals.
Isner will face the fourth-seeded defending champion Jack Sock of the United States, a 6-4, 6-4 winner over seventh-seeded Marcos Baghdatis of Cyprus.
In afternoon matches at River Oaks, Argentina's Juan Monaco beat fifth-seeded Sam Querrey 6-4, 6-4, and third-seeded Feliciano Lopez of Spain topped American Tim Smyczek 6-2, 6-3. The 32-year-old Monaco won the event in 2012.
In doubles, American twins Bob and Mike Bryan advanced to the final, beating Querrey and Steve Johnson 7-6 (5), 6-3. The Bryans have won the event five times and have 109 team titles.