Former world No 1 and her golf star boyfriend McIlory place a friendly bet on dietary habits

Caroline Wozniacki of Denmark aims to win a bet with golfer boyfriend Rory McIlroy of Ireland over their eating habits which she hopes will help her climb back to world No 1.

Wozniacki followed a 6-3, 7-5 victory over former French Open champion Ana Ivanovic on Thursday to reach the Dubai semifinals by revealing she has agreed to give up most of her favourite sweet treats.

In return, McIlroy is relinquishing his favorites - crisps, popcorn, sodas - apparently for a considerable amount.

"Let's just put it this way," Wozniacki said. "I wouldn't do it for a pair of sunglasses. I wouldn't put myself through that."

The Dane's dashing court coverage certainly gave the impression of immaculate conditioning as she worked her way into the last four in defense of her Dubai Open title.

Wozniacki's excellent performance suggested she may not suffer a disappointment similar to McIlroy, who led the field at the halfway stage of the Dubai Desert Classic the week before last, only to finish fifth.

"Actually I think I'm going to win," she said, referring again to the bet. "I'm stubborn so I'm not going to give up. And I trust him, yeah. He's such a bad liar, so I would tell right away if he had eaten something unhealthy."

On Thursday, her game showed characteristically resilient containment of many of her opponent's attacks, which were often dangerously hard-hitting from Ivanovic.

Wozniacki was also creative with her changes of pace, and alert to spot the openings to counter-attack.

However Ivanovic, who was playing well enough to get past fellow former French Open champion Francesca Schiavone in the first round, broke Wozniacki's serve three times in the second set, and might well have made significant progress had she managed to reduce her number of double faults, which reached a costly nine.

"I'm disappointed definitely," said Ivanovic, who began the week by restating her belief that she can one day reach No 1 again.

"I don't think I'm going to get much sleep tonight. But, you know, definitely motivated as well, because I feel like I achieved a fair bit this week."

Wozniacki's semifinal will be against Julia Goerges, the top-20 German, who overcame Daniela Hantuchova, the former world No 5 from Slovakia, 4-6, 6-3, 6-4

Although Goerges is unseeded, she has beaten Wozniacki on the past two occasions they have met, though both were on clay, a different surface from Dubai's. Wozniacki has won both their meetings on hard courts.

Earlier, another former world No 1 from Serbia, Jelena Jankovic returned to somewhere near her best form to upset the seedings and reach the semifinals.

It will be the eighth-seeded player's first semifinal of the year and also her best win for 12 months, a 6-4, 6-2 win over Samantha Stosur, the fourth-seeded US Open champion from Australia whom she beat here last year.

Jankovic succeeded despite a slowly healing muscle tear in her left thigh which, she says, was originally "5.5cm long".

She mostly adopted a more assertive style than she once had, controlling more of the rallies, and reducing the amount of court she needed to cover.

Stosur, by contrast, appeared subdued, looked travel-weary, and sounded as if she might be suffering from a cold. Having a base locally may have aided the livelier Jankovic significantly.

Jankovic next faces Agnieszka Radwanska, the fifth-seeded Pole, who allowed only three games to Sabine Lisicki, even though the Wimbledon semifinalist from Germany is this week at a career-high world ranking of 13.

Agence France-Presse