Although mandatory testing for illegal drug use is strongly opposed by most professional athletes' unions, the management of at least one league, the National Basketball Association, says it will press for just such a requirement when it begins contract negotiations with the NBA Players Association later this month.

In the National Football League, management contends it already has the authority to test players for drug use, but the union disagrees and says it may file formal grievances on the issue.

"It will very definitely be a collective-bargaining point in our negotiations over the new contract," said Jack Joyce, director of security for the NBA, who said he was speaking for NBA Commissioner Lawrence F. O'Brien. "We'd be very much interested in testing."

Larry Fleisher, who heads the NBA Players Association, said the union "is totally against testing.

"I think (Dallas Cowboy Coach) Tom Landry put it best when he said, 'We have not yet reached a police state in this country,' " Fleisher said.

Illegal drug use by professional athletes, an issue of increasing concern in recent years, has been the focus of particular public attention since publication in the June 14 issue of Sports Illustrated of a first-person account by Don Reese, a defensive lineman who played for Miami, New Orleans and San Diego, detailing his problems with cocaine.

Over the past several years, every major sports league has been embarrassed by news accounts of one or more of its athletes having become addicted to or dependent on illegal drugs, and periodically there have been suggestions that players be required to undergo periodic checks for drug use.

Essentially, debate pits the leagues' desires to maintain public confidence in the integrity and wholesomeness of their sports against the players' rights to privacy and a presumption of innocence. Proponents of testing also argue it would identify players in need of help.

Charles R. Jackson Jr., the National Football League's assistant director of security and the league's chief narcotics investigator, says the NFL proposed a program of regular drug testing of players in the mid-1970s but scrapped the idea in the face of militant opposition from the union.

Although the league did not pursue the testing issue after the union's initial objections, a number of clubs run regular drug checks as part of their routine physical examinations, over the objections of the NFL Players Association.

"NFL ballplayers are people who have the same rights as anybody else in society, and they don't deserve to be treated as racehorses or greyhounds," says Doug Allen, assistant to NFLPA Executive Director Ed Garvey.

Among the NFL teams to have tested players for use of illegal drugs as part of the routine physical exams are the Denver Broncos, the New England Patriots and the Cowboys.

Gil Brandt, the Cowboys' vice president for personnel development, is one who favors a more ambitious program of testing for drug abuse. "If you brought your squad in today and you tested them, and they knew you were going to test them next Tuesday and every week after that, I'll tell you one thing: it would stop it."

Brandt said the Cowboys did urinalyses on all their rookies when they reported for training camp two years ago, and they plan to do it again this year. But it's likely that to be effective any program would have to involve spot checks or weekly testing instead of a once-a-year physical, since many drugs become difficult to detect within a few days after use.

According to the National Institute on Drug Abuse, traces of cocaine, for example, disappear from the urine within 72 hours after use and from the blood stream within 36 hours.

Whether it's done once a year or once a week, however, there is no meeting of the minds between the NFL Players Association and the league on the issue of authority to test players for drugs.

Jack Donlan, executive director of the NFL Management Council, the league's labor negotiating arm, says the current collective-bargaining agreement already gives the clubs the authority to administer such tests.

Former Washington Redskin Brig Owens, now a special assistant to Garvey at the NFLPA, disagrees emphatically. Unless specifically authorized in a new contract, testing for drugs would represent a unilateral change in working conditions and would be an unfair labor practice, he said.

"They'd have a lot of problems with the players," said Owens.

Since the union first raised its objections to drug testing, the NFL has gone along with the NFLPA's position, a league spokesman said. In a letter prepared for response to public inquiries on the NFL's position on drugs, the NFL notes that it "does not employ urine tests for the detection of drug use and that the NFL Players Association has long been on record against such tests."

But the letter stops short of declaring the league actively supports such testing. Jim Heffernan, the NFL's director of public relations, said less than 100 copies of the letter have been mailed to the public.

Within the ranks of players, there are varied opinions on the issue of mandatory drug testing.

Mark Murphy, the NFLPA's player representative on the Redskins, said, "Most players are against it . . . It is assuming guilt by giving it. I think it could have some benefit if the reliability was good and it was done once a year and the players knew it was coming."

Redskins running back Terry Metcalf said "I wouldn't care one way or the other. If that's what they want to do, that's fine with me." Last week, Metcalf estimated that 50 percent of the players in the NFL and the Canadian Football League, where he played for three years, had experimented with illegal drugs. But later he said he was not sure his estimate was accurate and he had done no surveys.

Former Minnesota Vikings defensive end Carl Eller, a reformed cocaine user who is now an NFL consultant on drug-related issues, said he has mixed feelings about testing for drug use.

"I don't think athletes should be singled out," said Eller, who admits to once having had a $2,000-a-week cocaine habit. "But if a man is having a problem we would want to know about it and be able to help him."

In basketball, said NBA Players Association head Fleisher, "we'll fight it" if the league presses the testing issue in contract negotiations.

Last January, the issue of drug use in the NBA became the focus of public attention after Washington Bullets guard John Lucas admitted having a cocaine habit.

Asked how he would feel about mandatory testing for drug use, Bullets forward Greg Ballard said, "It's sad that it has to come down to asking the question, because I feel any kind of athlete who values his career and his life wouldn't touch the stuff.

"I'd have to be against it, because it simply shouldn't come down to that. I personally wouldn't want it because I've never dealt with drugs and I don't want anybody testing me like I had been. But if it's as rampant as some people say it is, then maybe some people need to be tested."

Marvin Miller, executive director of the Major League Baseball Players Association, said he would oppose any testing beyond a routine physical examination at the beginning of the season.

"If you're looking for something specific like illegal drugs, then testing is unnecessary," said Miller. "It's like checking a horse after a race. You're being a detective then."

Baseball Commissioner Bowie Kuhn commented through a spokesman only that, "We would consider urinalysis if it were necessary."

Both the National Hockey League Players Association and NHL Commissioner John Ziegler said testing players for drug use has not become an issue in that sport.

"We do not consider it a major problem," said Ziegler, who suspended New York Rangers right wing Don Murdoch for half a season after Murdoch was arrested in the spring of 1978, after the hockey season was over, for possession of cocaine.

"I would not be so naive as to think that nobody has experimented," said Ziegler. "But every player knows that if he gets caught, he's going to lose his right to practice his profession for a period of time."