Kim Clijsters feels she can up her game for semi

Kim Clijsters is confident of producing the improved performance she feels is required to beat Vera Zvonareva in the Australian Open semi-finals.

The Belgian overcame Agnieszka Radwanska 6-3, 7-6 (7/4) yesterday to join Zvonareva in the last four and set up a rematch of last year's US Open final which Clijsters won convincingly.

But with Russian Zvonareva gunning for revenge, third seed Clijsters knows she will have to improve if she wants to make it through to a meeting with either Li Na or Caroline Wozniacki.

She said: "Everything has to be better: serving, returning, the unforced errors. I am in the semi-finals, but I don't feel like I have played my best tennis.

"I feel like I am hanging in there, working hard to win my points. And sometimes that's probably even more of an achievement than winning your matches very easily."

Clijsters realises a meeting with Zvonareva, who beat her at Wimbledon en route to a final defeat to Serena Williams, represents a major step up in class from her previous matches, but she believes she can raise her level at the business end of the tournament.

"She is a player who will be very consistent throughout the whole match," she added. "She won't really mix her game up tremendously; she'll always give you the same kind of thing. I think she does that well.

"At the US Open I don't think she played her best tennis in the final and I was able to take advantage of that. It will be tough. There will be a lot of long rallies.But throughout the years I have always been able to lift my game when it is necessary."

Clijsters cruised through the first set against Radwanska, breaking four times to the Pole's twice, and took the match on a second set tiebreak after suffering a wobble which saw her opponent hit back from 4-2 down to win three games on the trot.

Zvonareva ended the run of Petra Kvitova 6-2, 6-4. "I had to stay aggressive," Zvonareva said. "She is such an aggressive player herself and you don't want her to keep going for her shots."