WASHINGTON (AP) _ President Reagan, saying rampant drug abuse is reaping ''sorrow and heartbreak'' across America, launched a campaign Monday to purge schools and workplaces of illicit drugs.

Reagan unveiled a six-point program to coax people off drugs and embraced a combination of mandatory and voluntary tests of both government and private employees to get the job done.

In a nationally broadcast appearance, Reagan credited his wife Nancy with working hard to get kids to say no to drugs, and said that ''starting today, Nancy's crusade to deprive the drug peddlers and suppliers of their customers becomes America's crusade.''

During a brief question-and-answer session, Reagan acknowledged that he had only recently taken a high-profile role in the administration's quest to combat drug abuse. ''We hadn't before put the effort that we recognize now, should be put ... and that is ... the time has come for a nationwide crusade,'' he said.

In the United States, there are an estimated 3 million to 5 million regular users of cocaine; 18 million to 20 million regular users of marijuana and 10 million alcoholics.

A senior administration official, briefing reporters later on the condition he not be identified by name, said, ''I don't think anyone has said make mandatory drug testing a condition of employment.'' However, the official added, ''We're going to ask corporate America to expand'' drug testing.

Reagan outlined six broad goals encompassing his plan to attack a growing problem that he said costs business $100 million a year.

Among them, he said, is a plan to create a drug-free workplace for all Americans, getting drugs out of schools, improving efforts to inform people of the dangers of drugs; stepping up law enforcement drug interdiction efforts and attempts to get other nations to cooperate, and ensuring drug treatment for people who need it.

But Reagan would not say how much the new initiative will cost, nor reveal what plans, if any, the administration has for asking Congress to improve new spending plans or supplement programs already in effect. He did say, ''the solution does not lie simply within the realm of government.

''It is time to go beyond government,'' Reagan said. ''All the confiscation and law enforcement in the world will not cure this plague as long as it is kept alive by public acquiescence. So, we must go beyond efforts aimed only at affecting the supply of drugs. We must affect not only supply, but demand.''

Reagan stopped short of announcing a program of drug screening for federal employees - a drug-fighting option that has been heavily publicized in recent days. But he said he has suggested that members of the Cabinet take tests, if that would set an example.

''I think we're pretty much agreed that mandatory testing is justified where the employees have the health of others, the safety of others, in their hands,'' Reagan said, referring to law enforcement authorities, air traffic controllers and the like in the federal workforce.

''On the other hand, I think we're pretty much agreed that what we should seek is voluntary'' testing among federal employees, with the notion of ''setting a pattern, an example, for society''

House Majority Leader Jim Wright, D-Texas, hailed Reagan's speech, saying, ''We are encouraged by the fact he is awakened to the reality of the problem, apparently he appreciates the dimensions of the problem.''

Wright told reporters he favors mandatory drug testing ''for anybody engaged in an occupation that involves public safety'' including air traffic controllers, bus drivers and ''people in the military involved in security matters.''

Wright, however, said the government's current annual expenditure of $3 million for drug education is like ''trying to fight a bear with a fly swatter.''

Sen. Orrin G. Hatch, R-Utah, speaking before Reagan's announcement, said that ''we'd like to reduce drug use in this country by 50 percent within the next three years.''

Said Sen. Paula Hawkins, R-Fla.: ''The White House today became the war room in the war on drugs.'' Describing Reagan's meeting to brief GOP lawmakers, Mrs. Hawkins quoted the president as saying that ''everybody understands what happened at Pearl Harbor, and this time it's going to be Pearl Harbor for the drug traffickers.''

Rep. Charles Rangel, D-N.Y., chairman of the House Select Committee on Narcotics Abuse and Control, said: ''I'm glad that he has said he has not come up with his strategy yet. That's what we lack, a national strategy.''

Rangel said the administration should devise military and economic sanctions against nations that refuse to cooperate with efforts to stamp out international drug traffic.

But Rangel added that ''to me war has been declared'' on the nation's drug problem. ''This would not be the first president who has been late in recognizing the seriousness of the problem,'' said.

Rangel said that at a White House meeting he attended earlier in the day, Defense Secretary Caspar Weinberger expressed willingness to increase the role of the military in combatting drug traffic into the United States.

Reagan lamented reports he said show that increasing numbers of children are ''being approached in the fourth grade'' by people seeking to peddle drugs, and he said the deaths of two well-known athletes have added to raising people's consciousness about the issue.

While the president said drug arrests and confiscations and interdictions are up, demand remains strong.

''We've waged a good fight,'' he said. ''And yet drug use continues, and its consequences escalate, claiming so many victims including promising young athletes, and bringing sorrow and heartbreak into homes across our country.''

He referred directly to the recent cocaine-related deaths of University of Maryland basketball star Len Bias and Cleveland Browns defensive back Don Rogers.

''We will offer a helping hand,'' he said, ''but he will also pressure the user at school and in the workplace to straighten up, to get clean.''