The amiable Belgian, who signaled her comeback from injury last year in Indian Wells in March before going on to win her first grand slam, said: 'It's something I was thinking about when I got injured [in 2004]. I was very happy that I was able to come back but because of the enormous amount of time [it takes], the exercise and the effort that I have to put in to being able to feel like I am feeling at the moment and to not have injuries, it's getting more and more difficult.'

'Every two months, it feels that I have to improve all the time and have to add something [to her game]. I told myself that I was going to do this for two more years. I am going to give myself 100 per cent while I am here and see how it goes,' said Clijsters, whose career has been marred by several injuries including a career-threatening wrist injury.

She said yesterday that the punishing schedule of playing on the tour was slowly taking a toll on her body and that she didn't want to be riddled with injuries later in life.

'The travelling is also very tough. I am not a very good flyer. When I get older and when I have kids one day, I would like to play and have fun with them without having to worry about having bad knees. I want to think about the future too.

'For me tennis is important but it is not the most important thing in my life. As long I have my family and my friends, that is a lot more important. I want to spend more time with them. I noticed last year when I was recovering from my injury, I was finding it harder and harder to leave home. There's two more years. There's a while to go,' she said.

Asked what the key to her success was last year, Clijsters said: 'It was a matter of time [of winning a slam] and everything falling to place too. After having my surgery [wrist] at the start of 2004, I realised that I was out for a long time and that I was making a lot of decisions for myself and although they were hard, they all turned out well and that gave me a lot of motivation.

'I started to play better and better and I was down during the French Open and Wimbledon but I kept going better and better and I had a very good end of the year.'

Despite her retirement plans, Clijsters said she was going to make the most of her remaining career, beginning with the Australian Open (January 16) in Melbourne.

'It's been a while since I was there. First of all, I am very happy to go out there again. It's great to play in Australia because I lived there for a long time. I have a lot of friends and I know a lot of people there. It's always nice to go to places where you know a lot of people.

'My goal next week is more to get used to the Australian summer again. I had a really good time at home [Belgium] and I really needed a break so I probably took a longer break this year than I did two years ago. But I felt my body really needed it.'

Clijsters, meanwhile, said Martina Hingis's comeback was 'exciting' but she said the Swiss ace would find it hard achieving glory again.

'I think it will be very hard for someone in her position to be ... a few years ago, being world number one and winning so many events and grand slams. It will be very hard for her to come close to achieving those results again. I haven't seen her play and I don't know what shape she is in but I am very excited. She's a great girl too and I am happy to see her back,' said Clijsters.