Sydney: Caroline Wozniacki powered through a training session in oppressive heat at the Sydney International on Sunday before revealing why she was so candid about her relationship with U.S. Open golf champion Rory McIlroy.   

After saying she was unaware that Petra Kvitova would overtake her as the world number one if the Czech left-hander won this week's Sydney International, Wozniacki then proceeded to happily answer a stream of questions about McIlroy.    

The highest-profile couple in sport are constantly photographed together, talk about each other in interviews, boast about the gifts they share and write to each other - for the world to see - on Twitter nearly every day.   

"It's very difficult to keep it really private because everyone knows who we are," Wozniacki told reporters in Sydney of the relationship.   

"People are interested. I don't mind if there's a camera here or there - it's fine. But we do have a line where certain things are private.    

"Something might come up and we say OK, we're going to keep this to ourselves. The rest is no big deal. Like, we have little bets. We had one bet about who was going to win a tournament first, and I did.    

"Right now we don't have any bets going on, though. I just think it's great that he's doing so well. I'm really happy for him."   

Wozniacki declined to reveal her prize for winning the bet but suggested it might have entailed a photograph of Northern Ireland's McIlroy, a Manchester United supporter, in the team shirt of her favourite English Premier League side, Liverpool.    

Wozniacki won a Liverpool shirt, signed by the club's midfielder Steven Gerrard, on court at the 2011 Qatar Open.    

"I can't tell you what I won," she said. "It's something I had to put on Twitter but I didn't do it because I thought I should be nice.    

"Actually, I still have that ace in my hand in case he's not nice to me." An incriminating photo, perhaps? "We're big fans of different football clubs, let's just put it that way."   

A Dream   

Back at the tennis, Wozniacki and Kvitova have first-round byes at the start of a week that could end with the Dane's 64-week stay as number one coming to an end.    

Asked if she was aware of that scenario, Wozniacki replied: "No. Now I am. It doesn't really matter. To be honest, I don't think about it. I do what I'm best at and that is playing tennis.    
"I enjoy being where I am. We have both enjoyed something very special at a young age. Petra has won Wimbledon and I've been number one for 64 weeks now and I think that's a great achievement.    

"It's always a dream to reach that ranking and I just have to keep concentrating on my tennis. That's all there is to it."   

Ana Ivanovic was a first-round casualty on Sunday, losing 7-6 (7-5) 6-2 to Lucie Safarova. Ivanovic's relationship with Australian golfer Adam Scott is the polar opposite to that of Wozniacki and McIlroy in terms of privacy.    

A question from the floor during her news conference: "Ana, Will Adam Scott be joining you in Melbourne for the Australian Open?" She said a polite 'yes'. No more discussion was entered into.

(Agencies)