SAN JOSE: Top seeds Andy Roddick and Fernando Verdasco booked their semi-final berths at the SAP Open ATP tennis tournament.

America's Roddick, seeking the fourth San Jose title of his career, defeated fifth-seeded Czech Tomas Berdych 7-6 (7/5), 7-6 (7/5).

Between them Roddick and Berdych belted 34 aces - 16 for Roddick and 18 for Berdych..

"He forced me to play well," Roddick said. "I made no bones about the fact that I would have to work my way into this event. You don't always have to feel comfortable to win a tennis match."

He next faces seventh-seeded compatriot Sam Querrey, a 6-4, 6-3 winner over Michael Russell.

Second-seeded Verdasco defeated Lithuanian qualifier Ricardas Berankis 6-3, 7-6 (7/5).

Berankis, ranked 225th denied Verdasco a break chance in the second set.

But the 19-year-old, who was the first Lithuanian-born player to reach the ATP Tour quarter-finals, couldn't hold off Verdasco in the tiebreaker.

The Spaniard said his sore right hamstring was improving.

"I've been getting treatment for it and that's all I can do," Verdasco said. "Since the first moment I played here it's feeling pretty good and even more so now."

Verdasco will have the advantage in experience over his semi-final opponent as well, when he takes on unseeded Denis Istomin of Uzbekistan.

Istomin, who had beaten fourth-seeded German Tommy Haas in the second round, downed sixth-seeded German Philipp Kohlshreiber 6-1, 1-6, 6-3 to reach the first semi-final of his career.

"I'm so happy - the first time in my career I play a semi-final," he said. "Today I played so well - I think it's the best match I played of my life."