DOHA, Qatar (AP)—U.S. Open champion Kim Clijsters defeated top-ranked Caroline Wozniacki 6-3, 5-7, 6-3 to win the WTA Championships final Sunday.

It is a third victory at the season-ending tournament for the 27-year-old Belgian, who was playing her first event since winning her third Grand Slam title at Flushing Meadows in September.

“It was a tough match,” Clijsters said. “It is disappointing for Caroline but she has a great future ahead. I’m glad I won and it must be disappointing for Caroline, but I don’t know how many more years I’m going to keep doing this.”

Wozniacki, 20, took over the No. 1 ranking from the injured Serena Williams this month, but was unable to back it up with a win in Doha and is also still without a Grand Slam title.

She has won the most tournaments this year—six—but seemed to crumbled in big tournaments and has a dismal career record of 15-24 against top 10 players. She has never beaten Clijsters, Justine Henin, Venus or Serena Williams.

“I’ve had a fantastic year,” Wozniacki said on Sunday. “I won six tournaments. I’ve beaten so many good players. You know, you cannot win every match. I’ve made the finals of the Championships, and I lost one match today. You know, I cannot do anything about it now. I will come back in the off season and train, but right now I’m proud of my season.”

Clijsters came to her defense, advising Wozniacki not to listen the doubters when she takes to the court in 2011.

“She will win a Grand Slam. She is too good of a player not to,” Clijsters said. “She’s young. She’s No. 1. I mean, you know, she’s too good of a player … She just has to keep working the way that she has been working. She’s been doing really good things, and the good things will keep coming then.”

Wozniacki’s shortcomings were on display Sunday when the 27-year-old Clijsters took a 2-0 lead on her way winning the first set, using a powerful forehand, well-timed backhands and her vast experience to overwhelm Wozniacki. She closed out the set by breaking Wozniacki for the third time.

The Belgian mother of one, who won the title in 2002 and 2003, went up 4-1 in the second, feasting on Wozniacki’s weak second serve and her inability to hit forehand winners. But Wozniacki fought back to tie the match at 5-5 and broke Clijsters to go up 6-5 on her way to winning the set when Clijsters hit long.

“Yeah, I think I just went behind the baseline a little bit too far. I think I let her dominate the rallies, and that was something I was doing well leading up to that point,” Clijsters said of her struggles in the second set.

“I felt that I was cutting the corners, being very aggressive, you know, making her move from side to side. And then I felt after a couple rallies, yeah, felt my legs just a little bit tired. Then you automatically become a little bit too defensive. I think that’s something that I realized, luckily, in time.”

Wozniacki came out strong in the third set, forcing No. 4-ranked Clijsters to make four unforced errors to win the first game. But Clijsters didn’t panic, settling down to go up 2-1. That prompted Wozniacki’s coach, her father Piotr, to come out and give his daughter a courtside pep talk as she rested a bag of ice on her head. It didn’t do much good.

Clijsters kept the pressure on, moving Wozniacki around the court and hitting several powerful forehands to go up 5-2. Wozniacki grabbed a game back before Clijsters won it when Wozniacki hit a return into the net.

“In the third set, you know, it was very close,” Wozniacki said. “She played really well, especially in the important moments. Definitely, the experience, you know, mattered a little bit today.”

Clijsters’ victory in the WTA’s most lucrative tournament ends a topsy-turvy week in which she arrived with lingering doubts about her physical fitness. After her second successive U.S. Open victory, she suffered a foot infection which kept her out of action for six weeks.

She didn’t show any signs of rust when she swept aside an ailing Jelena Jankovic in her opening match. But fatigue seemed to get the best of Clijsters in her loss to No. 2-ranked Vera Zvonareva Friday, after she had seen off Victoria Azarenka in a three-set match the night before that lasted well past midnight.

Then on Saturday, the car taking Clijsters to the stadium was involved in what she described as a “scary” accident. She was unhurt, while her manager suffered minor cuts, but the Belgian still came out and beat Australian Sam Stosur in her semifinal match.