"I still have that craving,'' the 25-year-old Belgian said Thursday. "I look forward to the challenge.''
Clijsters, who retired in May 2007 to get married and start a family, announced her comeback at the tennis facility in Bree, Belgium, where she has been practicing recently.
She said she has already asked for wild cards for WTA hard-court tournaments in Cincinnati and Toronto in August and the U.S. Open.
"I want to be back at my peak as soon as possible, but I know that is not logical to ask that,'' Clijsters said. "I will have to take it match by match.''
The U.S. Tennis Association is setting aside a spot in the main draw for Clijsters at the U.S. Open, which starts Aug. 31.
"We have been in contact with Kim regarding her comeback and have committed a 2009 U.S. Open wild card to her,'' tournament director Jim Curley said. "As a past U.S. Open champion and former world No. 1, Kim has been a great ambassador for our sport. We are excited about Kim's return to tennis and look forward to welcoming her to New York this summer.''
Clijsters won the 2005 U.S. Open for her one Grand Slam title. She won 34 career titles overall and was runner-up in four Grand Slam finals.
Rising to the top at the same time as another Belgian who retired early, Justine Henin, Clijsters held the No. 1 singles ranking for 19 weeks.
"I am not coming back to lose in the first rounds,'' she said. "Otherwise I might as well go on holiday.''
Clijsters returns at a time when the WTA tour is wide open and without a single player dominating the rankings.
"I am amazed how many players I don't even know,'' she said. "There are even many names I do not know how to pronounce.''
Clijsters, who is married to American basketball player Brian Lynch and gave birth to her daughter Jada last year, is convinced she has the maturity now to juggle marriage, motherhood and top tennis.
"Now I have the right balance and I feel good,'' she said.
Clijsters refused to commit herself beyond the U.S. Open, preferring to make an assessment at that stage.
"One year, two or three, it is far too early to start answering those questions,'' she said.
Flashing her disarming smile and with her blonde curls tied in a ponytail, Clijsters exuded the easygoing charm which made her a fan favorite around the world.
Her career was marred by a series of injuries, including to her hip and back.
"I know a lot, lot more about my body,'' Clijsters said, adding that she has an exercise regimen designed to prevent injuries.
Clijsters was already set to join Steffi Graf, Andre Agassi and Tim Henman for a series of exhibition matches at Wimbledon on May 17 to test conditions under the new retractable roof on Centre Court.
She said it was while preparing for the Wimbledon exhibition that the competitive edge came back.
Soon, she was spotted at the training center putting in long hours. When she was seen at the basketball court to support her husband, she had that lean streak in her face again.
"I have never trained harder,'' she said.
Clijsters also is scheduled to play an exhibition June 14 against Michaella Krajicek in the Netherlands, along with two matches for the St. Louis Aces of World Team Tennis in July before making the big jump back to the WTA Tour.
