Roddick came up with four aces in the second-set tiebreaker and defeated Safin 7-6 (7), 7-6 (4) in a second-round match at the ATP Masters Cup Championships on Thursday.

The second-seeded Roddick remained on course for a weekend meeting with No 1 Roger Federer, already assured a semifinal berth in the round-robin format.

Federer was scheduled to play Carlos Moya later Thursday. Federer beat Roddick in the semifinals of last year's Masters Cup. Roddick has a 2-0 record in the Blue Group. The top two players from the Blue and Red groups meet in Saturday's semifinals.

Roddick and Safin remained on serve throughout the second set, though Safin had to save two break points in the third game and Roddick came back from three break points to hold in the 12th game and force the tiebreaker.

"I felt lucky to get through the first set," Roddick said. "The rest of the match, I couldn't ask for more. I thought that was some high-level tennis."

Roddick broke from a 3-3 deadlock in the second-set tiebreaker with a 121 mph ace and didn't trail again. Safin made a running forehand error to bring on match point, and Roddick's 118 mph ace closed it out.

Roddick had to struggle to reach the second tiebreaker, overcoming three break points in the final game of the set. After Safin got the third break point, Roddick served an ace to pull even. Roddick then went ahead on Safin's service return into the net. After the shot, Safin broke his racket by slamming it to the court.

"I was just a bit unlucky, it's like I always say, tiebreaks are a lottery," Safin said. "I did everything right. I can't say that I made a huge mistake. But I had chances before to break him."

In an earlier match, Tim Henman overwhelmed Guillermo Coria 6-2, 6-2. Henman evened his record at 1-1, while French Open finalist Coria, still recovering from shoulder surgery, dropped to 0-2.