NEW YORK, (Reuters) – Roger Federer and Serena  Williams will begin the defence of their U.S. Open titles at  Flushing Meadows today, while Kim Clijsters returns to  grand-slam tennis for the first time in two years.

World number one Federer, chasing a modern-day record sixth  straight title at Flushing Meadows, plays American wild card  Devin Britton in the first round in his first grand-slam event  since the birth of his twin daughters last month.

The Swiss, bidding to add the U.S. Open to the French Open  and Wimbledon titles he won earlier this year, is hoping to  equal the mark set by American Bill Tilden in the 1920s.

Moreover, Federer can extend his record of grand-slam wins  to 16 by winning in New York.
It is a far cry from 12 months ago when he arrived in New  York without having won one of the first three grand slams for  the first time since 2002.

“I’m just more relaxed this time,” he said. “I’ve already  won slams this year. That takes away pressure from having to do  well here, like the feeling I had last year, not having won a  slam last year, trying to get the first one.

“This year is different. I feel like I’m playing great. That  gives me obviously a lot of confidence and relaxes my mind.”

Fifth seed and 2003 winner Andy Roddick, the runner-up to  Federer at Wimbledon, opens his campaign against German Bjorn  Phau.

Women’s champion Serena Williams, seeded second, plays  fellow American Alexa Glatch in the first round.

Victory for Williams over the next two weeks would give her  a 12th grand-slam title, equalling Billie-Jean King’s mark.

Serena’s sister, third seed Venus Williams, plays the first  night match against Russian Vera Dushevina, while the tournament  begins (1500 GMT) with the return of Clijsters after two years  off the tour.

In her third event back, the Belgian former world number  one, who had her first child 18 months ago, plays Viktoriya  Kutuzova of Ukraine.

Eighth seed Victoria Azarenka, Flavia Pennetta (10) and  Amelie Mauresmo (17) are also in first-round action today.