NEW YORK (AFP) Defending womens champion Kim Clijsters, 16-time Grand Slam winner Roger Federer and Venus Williams will provide the first-day fireworks when the US Open begins on Monday at Arthur Ashe Stadium. Belgian second seed Clijsters, whose past two US Open appearances in 2005 and last year have resulted in her only Grand Slam crowns, will open against Hungarys 104th-ranked Greta Arn. Federer begins his quest for a seventh consecutive US Open final and his sixth title in seven years on the Flushing Meadows hardcourts against Argentinas 94th-rated Brian Dabul. The 29-year-old Swiss superstar lost to another Argentine foe, Juan Martin Del Potro, in last years US Open final, but Del Potro will not be defending his crown due to a wrist injury. Reigning Australian Open champion Federer has shrugged off critics who say he is past his prime since his run of 23 Grand Slam semi-finals in a row was stopped at the French Open quarter-finals by Robin Soderling, a fifth-seeded Swede who could play Federer in the US Open quarter-finals. At times I took it as a compliment, Federer said. I was No. 2 in the world and winning one or two Slams a year and I was on the downslide. You cant really take it too seriously to be quite honest. You cant win 12 tournaments every season. Thats clear for me. I spoiled myself by playing so well. If its two or four or six its still a good season depending on how well you are feeling, how you are evolving as a player. US third seed Williams, a seven-time Grand Slam champion with US Open titles in 2000 and 2001, will open against Italys 65th-ranked Roberta Vinci. Williams won their only prior match in this years third round at Miami. Williamss younger sister, world number one Serena Williams, will not be competing due to a right foot injury that has required surgery. Serena won the Australian Open and Wimbledon titles but has been nagged all year by injuries. While Serena Williams will not be on the court, the line judge she screamed at last year during a profanity-laced tirade, Shino Tsurubuchi, will be back on the sidelines serving as a match official at this years US Open. In a semi-final against Clijsters, Serena Williams was called for a foot fault that sparked her to threateningly approach Tsurubuchi, who went to the umpire to report a code violation that saw Williams lose on a penalty point. Tsurubuchi will rotate between mens and womens matches as any other line judge at the years final Grand Slam event. The only former US Open mens champions in this years field aside from Federer will both be in action Monday as well. Australian 32nd seed Lleyton Hewitt, the 2001 winner, will face 107th-ranked Frenchman Paul-Heri Mathieu while US ninth seed Andy Roddick, the 2003 champion, will meet Frances 78th-ranked Stephane Robert. Meanwhile, Caroline Wozniacki is not feeling the pressure of being a top seed at a Grand Slam event for the first time, confident she can repeat her 2009 run to the final at this years US Open. The 20-year-old Dane who lost to Kim Clijsters in last years final will begin play Tuesday at the years final Grand Slam event as the top seed because world number one Serena Williams is sidelined by a right foot injury. World number two Wozniacki comes into the Flushing Meadows fortnight having won last Mondays rain-delayed WTA final at Montreal and the New Haven WTA final on Saturday, boosting her confidence she can live up to her seeding. I dont feel theres any pressure, Wozniacki said Sunday. Pressure is when you are put on the spot and you dont feel like you belong there, dont think you deserve to be there. I feel like I deserve to be where I am and Im feeling comfortable. Wozniacki, who has 10 career titles, nearly completed a dream run through the womens field last year and is excited about her chances this time.