Novak Djokovic, Roger Federer advance

DUBAI, United Arab Emirates -- Novak Djokovic defeated fellow Serb Janko Tipsarevic 6-1, 7-6 (6) Thursday to set up a Dubai Championships semifinal with Andy Murray, who he beat in a marathon five-setter at the Australian Open last month.

Roger Federer will face Juan Martin del Potro in the other semifinal at Aviation Club. Del Potro beat Jo-Wilfried Tsonga 7-6 (1), 6-2 for the second time in two weeks.

Murray advanced by defeating fifth-seeded Tomas Berdych 6-3, 7-5. Federer had another routine encounter, stopping Mikhail Youzhny 6-3, 6-4.

The top-ranked Djokovic, gunning for his fourth Dubai title in a row, broke the seventh-seeded Tipsarevic twice and closed out the first set when his opponent returned long. Tipsarevic rallied the second set, holding his serve throughout and taking a 4-1 lead in the tiebreaker. Tipsarevic missed a set point at 6-5 when he double-faulted, and Djokovic won the next two points.

"We know each other really well," Djokovic said. "We both got a little bit nervous toward the end, I guess, and it was just luck to prevail."

Tipsarevic admitted nerves got the better of him in the second-set tiebreaker, but not because he was facing a friend.

"Obviously, it's like little butterflies in the stomach having the set point on 6-5 in the tiebreak after a one-hour set," Tipsarevic said. "It's not only against Novak. It would have happened against anyone. Normally you're trying your best on this point. It's just that I tried too much for no reason."

Murray has lost his last three matches against Berdych but broke early to take control of the first set.

In the second, the players twice traded breaks of serve. Murray broke to go up 6-5 but squandered six match points before clinching it when Berdych hit long.

"That's one thing I've always been very comfortable with, closing matches out," Murray said. "I played three great serves to bring it to 40-Love and then missed a few first serves in a row and he went for some big shots. Then once you're back at deuce you're thinking, 'God, I've just blown three match points.' So you kind of just want to try get through it if you can."

Berdych had a chance to break to take the second set to a tiebreaker. Murray delivered a serve that was initially called out but overturned on review. Umpire Mohammed Lahyani gave the point to Murray, leaving Berdych angry because he felt the point should have been replayed.

Lahyani argued that Berdych had already played his return into the net when the call came.

"When the point end up like this, actually this is something you don't expect at all," Berdych said. "You just trying to be focus on the game and go point by point, and then something like that came and you know you are right. What you can do?"

Murray said he was looking forward to his semifinal clash against Djokovic.

"I would like to get a chance to play him again," Murray said. "Before the Indian Wells-Miami stretch it would be good to see exactly what I need to work on, where my game is. I had a great match with him in Australia, and hopefully I can reverse the result tomorrow."

Federer, who is looking for his fifth Dubai title, defeated Youzhny for the 12th straight time. He has had similar success against Del Potro, carrying a 9-2 record into their match. But one of those losses was in the 2009 U.S. Open final, a win that will be on the Argentine's mind Friday.

"I always think about that final. After the final in Rotterdam (last month), he (Federer) told me 'You have the big one, so don't be sad,'" Del Potro said. "All the matches are different, all tournaments are different, and I'm trying to find a way to beat him again. It's really difficult for me, his game. He plays slices, drop shots, and he's one of the best in history. So I just want to be ready for a fight."