In what will be the first program of its kind in major league baseball, the Baltimore Orioles will announce Thursday that they've established a program of voluntary player drug testing, sources said tonight.

Player participation in the program is voluntary, but once a player signs up he can't back out, sources said. In the program, players will be tested three to six times per season and the test will be administered through Johns Hopkins University.

The idea for the plan originated with Baltimore attorney/agent Ron Shapiro, who represents 20 Orioles. Shapiro said all of his clients, which include first baseman Eddie Murray and shortstop Cal Ripken, will participate in the plan.

The Major League Baseball Players Association has opposed drug testing, but Shapiro said he has discussed the plan with Donald Fehr, executive director of the union. "He won't support it," Shapiro said, "but more important, he won't oppose it."

Fehr was unavailable for comment tonight.

A random sampling of players tonight found widespread support for the plan, although all had reservations about how it would work. One reason the union says it has opposed drug testing is that it didn't think the results would be handled the same for all players, and that remains a concern for some Orioles.

Like other clubs, the Orioles have included clauses for mandatory drug testing in all contracts this winter. But the union has filed a grievance claiming such clauses are illegal because only benefits can be added to the standard player contract.

"We consider it a benefit if we can help a guy with a problem," Orioles General Manager Hank Peters said.

The Orioles conducted spot checks of their minor league players last summer, and Peters said "not one guy who came up positive denied he had a problem."

Baseball is without any kind of drug program since the owners dropped out of the Joint Drug Agreement last October. Under that program, players with a problem could get help without losing any salary or being suspended.

Last summer, though, Commissioner Peter Ueberroth and the owners began pushing for a program that included spot checks. But the owners said the players stonewalled every effort. Since that time, the two sides have gone in different directions. The owners have inserted drug-testing clauses in contracts, and the players announced a program of public service announcements on the dangers of drug use.

"Its not a program without testing," Peters said.

In interviews late last season, several Orioles, including Murray, said they wouldn't volunteer for such a program. But Shapiro says that when the plan is announced Thursday, he will have 100 percent support from the players he represents.

"I'm not for the test but I'm going along because something has to be done," said Murray. "I want people to know the game is clean."

Orioles player representative Scott McGregor has been distributing two-page summaries of the program to his teammates in recent days and will appear with Peters at Thursday's news conference. McGregor, who refused to comment on the program today, has been a strong supporter of drug testing for months.

"I have nothing to hide and I think the tests are a good idea," he said last summer. "It gets baseball out from under this cloud."

Another Oriole, who asked that his name not be used, said: "I don't know what I'm going to do. I know baseball has an image problem with drugs, but I don't like feeling that my privacy is invaded. But if I don't go along, I'm going to be declared guilty anyway."