WASHINGTON (AP) _ A fierce dispute over the future of organized crime strike forces, the Justice Department's shock troops in the war against the mob, is heating up within the law enforcement community.

''This is a turf fight - it's as simple as that,'' says Philadelphia attorney Peter Vaira, a former strike force chief in that city who once headed the President's Commission on Organized Crime.

A Senate Judiciary Committee hearing is set for July 21 on the strike forces, teams of prosecutors initially established by Robert F. Kennedy at the Justice Department to specialize in organized crime and labor racketeering.

Currently based in 14 cities, they have compiled a record of achievements that even critics call impressive.

Organized crime leaders from Boston, New York, Philadelphia, Cleveland, Chicago, Kansas City and other cities are currently serving long prison terms as a result of strike force investigations.

Indeed, Boston attorney Jeremiah T. O'Sullivan, a former New England strike force chief, recalls a wiretap as early as 1981 in which hoodlums were heard to speak hopefully of chances that the strike forces would be disbanded.

Actually, the strike forces will be disbanded - in effect, if not in name - under a plan announced by Attorney General Richard Thornburgh, say supporters of the units within the legal community.

Thornburgh plans to place the strike forces, which now report directly to Washington, under the control of presidentially appointed U.S. attorneys, who traditionally have been the top federal prosecutors in their communities.

''I think it's an unfortunate decision,'' says Temple University law professor Charles Rogovin. ''Essentially what is being done is the dismantling of an apparatus that has really developed a remarkable kind of expertise.''

Former strike force officials say there have been resignations in Boston, Brooklyn and Los Angeles that in part were caused by Thornburgh's plan. In fact, O'Sullivan says it was ''one factor'' in his own departure.

He says he had battled for years to hold the strike forces together and, ''I just didn't have the energy to fight this fight one more time.''

New York attorney Edward A. McDonald, formerly chief of the Brooklyn strike force, is critical of what officials ''euphemistically call the merger of the strike forces. I like to call it the abolition or destruction of the strike forces.''

Nonsense, retort Justice Department officials. They say the plan guarantees that the strike force will remain intact but under control of U.S. attorneys, thus ending squabbling and rivalries.

''Are we going to spend 30 percent of our time arguing over whose case this is? Or are we going to make the case?'' asks Edward S.G. Dennis, assistant attorney general and No. 2 official at the Justice Department.

Praise is coming from virtually all of the nation's U.S. attorneys. ''I think this is an excellent idea,'' says Chicago U.S. Attorney Anton R. Valukas. ''What it would do is substantially increase our ability to continue the war on organized crime.''

Gone are the days when U.S. attorneys lacked the sophistication to launch the complex undercover investigations needed to catch mobsters, says Valukas. He points to the ''Operation Graylord'' cases that revealed widespread bribery in Chicago courts and resulted in conviction of scores of judges, lawyers and court officials.

U.S. Attorney James Richmond of Hammond, Ind., chairman of the 15-member Attorney General's Advisory Committee, points to stunning successes of Rudolph Giuliani and other U.S. attorneys in New York, where the strike force was merged into the U.S. attorney's office. The arrangement has produced some spectacular successes against organized crime.

''This will certainly not diminish the fight against organized crime,'' says Richmond. ''It will enhance it.''

Current strike force attorneys have remained silent in the debate. One current strike force prosecutor, who asked not to be identified by name, cited a March 9 memo from Dennis warning that violations of publicity guidelines could mean firing.

Former strike force chiefs, however, have mounted a lobbying campaign designed to save their old program. They say Thornburgh has carried a longstanding grudge against the program.

''He had innumerable run-ins with the Pittsburgh strike force when he was U.S. attorney in the early 1970s and it left a bad taste in his mouth,'' says Douglas Roller, former strike force chief in Chicago.

And questions have been raised concerning the strong political ties that usually mark relations between U.S. attorneys and the local establishments in their communities. Indeed, the post of U.S. attorney has been a launching pad for many political careers.

''The loyalties of U.S. attorneys are to the senators who nominated them,'' says Bruce Fein, a former Justice Department official and now a conservative analyst of the federal court system.

The issue came up at a June 20 hearing of the House criminal justice subcommittee when Rep. George Sangmeister, D-Ill., questioned Dennis.

''There are always a lot of calls like, 'Old Moe has been a good contributor to the party for all these years and it's a shame that you're doing to him what you are,''' Sangmeister said. ''I think the U.S. attorney should be completely absolved from that.''

Dennis suggested that in such a case the U.S. attorney might recuse himself - bow out to avoid a conflict - and let an aide make the decision.

''The U.S. attorney is not going to recuse himself because somebody down in the party says take it easy on Moe,'' Sangmeister shot back. ''You don't recuse yourself for stuff like that.''