Tuesday, August 1 2006 19:03 Hrs (IST) - World Time -

Washington: Defending champion Andy Roddick withdrew from the ATP Washington Classic on Monday due to a lower left back injury suffered last week in Los Angeles, casting doubt on his US Open fitness.

The 23-year-old American practiced for 30 minutes and felt pain despite four days of rest and treatment, so the second seed elected to pull out and improve his chances of being in top form for the year's final Grand Slam tournament.

"The last thing I want to do is reinjure it with the US Open around the corner," Roddick said.

"It's disappointing I won't get to defend," he said.

Roddick said there is no timetable for his return but still intends to play next week in Toronto and the following week in Cincinnati.

Roddick the lower left back strain during a 6-7 (3/7), 6-3, 6-2 second-round triumph over US wild card Scott Oudsema last week in Los Angeles, pulling out before a scheduled quarter-final match.

Lucky loser Jan-Michael Gambill of the United States replaced Roddick in the draw. He will face Serbian Janko Tipsarevic on Wednesday.