Cincinnati, Ohio - Kim Clijsters returned to a WTA quarter- final for the first time since early 2007 as her comeback to tennis continued full throttle Thursday at the Cincinnati Open.

The 26-year-old Belgian, who retired in May 2007 to get married and have a baby, has shown that her form has not deserted her, defeating current French Open champion Svetlana Kuznetsova 6-4, 4-6, 6-2.

Five-time Wimbledon champion Venus Williams was stunned in the third round, losing for the fourth time in seven meetings with Italian Flavia Pennetta 7-6 (7-2), 6-4.

Pennetta won the title in Los Angeles last week and has now claimed 14 straight victories, including a clay title in Palermo last month.

Clijsters, the 2005 US Open winner, lost serve three times but broke Kuznetsova five times to advance in her first tournament back in action.

Clijsters acted upon her desire to get back into the sport after resuming training for an exhibition series she played last May to mark the debut of the new Wimbledon centre court roof.

The Belgian, winner of 45 singles titles, announced her comeback effort five months ago.(dpa)