EAST RUTHERFORD, N.J. (AP) New Jersey Nets center Alonzo Mourning is leaving basketball again because the kidney disease he's had for three years is worsening and he needs a transplant.

The announcement Monday came just a few months after Mourning signed a four-year contract with the Nets believed to be worth $22 million. The four-time All-Star sat out all of last season and large portions of two of the last three years because of the kidney ailment, focal glomerulosclerosis

The team said Mourning needs a transplant ``in the near future'' and that a nationwide search is under way for a prospective donor.

``Alonzo is a true champion and a very courageous athlete who attempted to defy the odds with his comeback to the NBA,'' Nets president Rod Thorn said. ``Unfortunately, his medical condition will not allow him to continue his basketball career.''

Dr. Gerald Appel of Columbia University Medical Center said Mourning's kidney function has deteriorated rapidly in recent weeks.

``It is no longer medically safe for him to play basketball,'' Appel said. ``Although he still feels well, the chemical imbalances in his blood make it dangerous for him to play.''

Mourning played in 12 games for the Nets this season, averaging a disappointing 8 points and 2.3 rebounds in 17.9 minutes. His career averages were 20.3 points and 9.8 rebounds per game coming into this season.

He was in his 12th season in the NBA, having previously played for the Charlotte Hornets and Miami Heat. He also was a member of the 2000 gold medal-winning Team USA Olympic squad.