New Jersey Nets guard Micheal Ray Richardson was banned from the National Basketball Association for at least two years after he tested positively for cocaine, NBA Commissioner David Stern announced today.

Stern called it "a tragic day for Micheal Ray Richardson, nothing less than the destruction by cocaine of a once-flourishing career."

Richardson, 30, was tested by Nets team doctor Dennis Quinlan Thursday and the results were verified Monday night.

Richardson's positive testing constitutes a third offense under the NBA's anti-drug policy that began Jan. 1, 1984. Stern called the action a permanent dismissal, although Richardson can apply for reinstatement after two years.

Richardson was informed of his disqualification this morning by Horace Balmer, the NBA's assistant director of security. "He was upset," Balmer said. "He denied use of cocaine ."

The Nets said they did not plan to appeal the ban. But his agent, Charles Grantham, said Richardson wants to contest the dismissal.

"He categorically denies taking any drugs," said Grantham, adding he would have an independent party review the results. "I just can't take the test results at face value. I'm not going to desert him."

Stern said the latest drug test was ordered last week after Richardson was arrested for allegedly trying to break into his home in Mahwah, N.J. Richardson said he did not know his wife Leah had obtained a court order barring him from the property.

The Nets have paid for Richardson's drug treatments since May 1983, and Stern said they would continue with his rehabilitation even during his permanent suspension.

When Richardson tested positive for drug use early last month after a five-day disappearance, the league ruled it was his second violation, because the two previous times he has undergone treatment were before the official start of the drug program.

After Richardson failed to appear for a Feb. 12 doctor's appointment for the flu, he was tested for drugs and the results were negative.

"We've tried everything within our power," Bernie Mann, president of the Nets, said. "It's something that nobody's too happy about. . . . When I found out the league tested positive , it broke my heart."

"I saw him for a couple of minutes this afternoon. He just felt . . . terrible," Lewis Schaffel, executive vice president of the Nets, said of Richardson. "Sometimes, I feel no one can feel worse than we do . . . . We took three years to give him all the support and guidance. We sent him to the best rehabilitation center in the country. We had all the support systems here," Schaffel said. "Ultimately, we all failed."

Officials around the league expressed sympathy for Richardson personally, but supported the ban.

Pat Williams, general manager of the Philadelphia 76ers, said Richardson "got enough chances, got enough warnings" and that the NBA's drug policy is "more than fair to the players."

Portland Trail Blazers Coach Jack Ramsay said, "It's too bad to see a player lose out on his career, but it's not as if he hasn't had chances to straighten out his life. I think somewhere, for his benefit as well as for the benefit of the sport, this kind of thing has to happen."

Richardson, in the first year of a four-year $3 million contract, has played for the New York Knicks, Golden State Warriors and Nets in eight seasons in the NBA. In 47 games this season, he was averaging 15.7 points, 7.2 assists, 2.7 steals and 5.4 rebounds. He was an all-star four times, from 1980-82 and in 1985 when he also was Comeback Player of the Year.

Richardson is the first active player banned under terms of this agreement. John Drew, formerly of the Utah Jazz, also is a three-time offender but was not under contract at the time of the third incident. He is now playing for Wyoming of the Continental Basketball Association.