Andy Roddick celebrated his 28th birthday today, but admits time is running out for him to add to his sole Grand Slam title.

Roddick won the US Open in 2003 but has been unable to break the dominance enjoyed by Roger Federer and Rafael Nadal since, losing three Wimbledon finals to Federer - most famously 16-14 in the fifth set of an epic contest last year.

And asked about his sense of urgency to claim another of the sport’s four biggest titles, Roddick admitted: “It’s always there. Birthday or no birthday, you come in to try to win one.

“To be honest, I don’t think too much about age, number, whatever. I’ll play till I can, until I feel like I shouldn’t any more. But the urgency is always there.”

Ninth seed Roddick begins his campaign with the third match on the Arthur Ashe Stadium today, taking on France’s Stephane Robert after fellow American Melanie Oudin faces Ukraine’s Olga Savchuk and defending champion Kim Clijsters plays Hungary’s Greta Arn.

Clijsters is ranked second this year behind world number two Caroline Wozniacki, the player she beat in last year’s final who comes into the event on the back of two tournament wins in six days.

“Definitely the finals here last year gave me a lot of confidence and the belief that I could do it,” said Denmark’s Wozniacki. “I just kept working hard and kept improving and I’m really happy to be back. Hopefully I can do well again this year.

“I feel like I’m playing better and better. The last two weeks, or actually four weeks, have been great for me. I’ve been winning a lot of matches, so that’s definitely something that brings up the confidence.

“It’s tough to compare myself to one year ago, for example. But I definitely think that I’ve improved in many aspects. I think that’s a positive problem to have, that I play many matches. That means that I’m winning.

“After Wimbledon I had five weeks off where I didn’t play anything and just practised, so that was a great feeling for me to get back on the match court and back in the match intensity.

“I actually feel great. I feel in good shape. I don’t feel tired, so I’m really happy. To be the number one seed at a Grand Slam, that feels good.

“But to win the matches I still have to play well. I still have to win seven matches to win a Grand Slam, and that’s not easy.”