Defense Secretary Caspar W. Weinberger's plan for deployment of a limited, space-based defense against ballistic missiles in the mid-1990s has run into strong opposition from senior military officials and Pentagon scientific advisers, according to U.S. officials and congressional sources.

These opponents in the military establishment charge that Weinberger's plan will absorb tens of billions of dollars that the Defense Department should spend on other armaments, and also that the system the secretary wants to deploy will not be ready on time or provide enough protection to make it worth the expense.

These criticisms have become more urgent in response to a quiet effort by Weinberger and Lt. Gen. James A. Abrahamson, director of the Strategic Defense Initiative (SDI) Organization, to obtain preliminary approval for the mid-1990s deployment scheme this week from the Pentagon's senior group of decision-makers for new weapons systems, the Defense Acquisition Board.

This approval by the board, which includes senior Army, Navy, Air Force and Joint Chiefs of Staff officials, is seen by Abrahamson as a means of raising the stature of the controversial SDI program and winning additional support from Congress, the officials said.

"Until now, we've been like pariahs in this {Pentagon} building," an SDI official said last week. "No one has really taken us seriously, and we've been pretty much alone."

Abrahamson has said the deployment scheme will cost $40 billion to $60 billion, and that it will involve putting hundreds of satellites into orbit with small rockets to try to shoot down Soviet missiles shortly after they are launched. The system, which Abrahamson says could be deployed beginning in 1994, would be supported by additional satellites for communication and surveillance, and complemented by hundreds to thousands of ground-based rockets aimed at Soviet missiles missed by the space-based rockets.

The system would be designed to protect a limited number of military installations, not cities, although it could later be supplemented by more effective defenses. A formal U.S. decision to go ahead with it -- which even proponents say is several years away -- would require renunciation of the 1972 Antiballistic Missile (ABM) Treaty, a step that makes congressional approval highly problematical.

Members of the Joint Chiefs of Staff have criticized the cost of the deployment plan, which they estimate as much higher than what Abrahamson has publicly stated. During preparations for a secret meeting of the Defense Acquisition Board on Tuesday, they also criticized the scheme on the grounds that it would destroy only a small portion of a massive Soviet attack.

A panel of the Defense Science Board concluded recently in a secret report for the board's chairman, Under Secretary of Defense Richard P. Godwin, that years of additional research are needed to determine if the deployment plan will work, according to knowledgeable officials. The panel also concluded that key missile defense systems may not be ready for accelerated testing and demonstration as Weinberger and Abrahamson have urged.

This new scientific criticism comes on the heels of a strong attack on the administration's timetable for SDI by the premier group of U.S. physicists, the American Physical Society, and in the midst of a congressional fight over whether the administration should be allowed to conduct space experiments that arms control experts believe are banned by the ABM Treaty.

The criticism has unsettled SDI officials who want the acquisition board's stamp of approval for more intensive missile defense work, the officials said. But both the JCS and the scientific panel are said to be under strong pressure to change their positions, and the officials said the board is unlikely to reject outright an idea that Weinberger and President Reagan enthusiastically support.

Although the "specific proceedings and recommendations" of the board will be "classified to protect national security," according the SDI office, a senior official involved in the program said he expects the board to approve by the end of July a rough "architecture" or basic design for the mid-1990s deployment scheme, a tentative budget plan and a testing plan leading up to a formal decision to develop the system several years from now.

"And when they do, it's really going to legitimize our program," the SDI official said.

The prospect of a decision by the board to endorse Weinberger's plan has created anxiety on Capitol Hill among SDI skeptics such as Sen. Albert Gore Jr. (D-Tenn.), who wrote to Godwin last week seeking his assurance that "Congress will not -- as a result of the board's meeting -- be suddenly confronted with a sea change in SDI, moving it from a research program to a weapons system on the way to development and deployment."

A White House official who has followed the debate said it reflects in part a fundamental split between military and civilian Defense Department officials over the relative importance of offensive and defensive weapons that began with the president's pathbreaking "Star Wars" speech in 1983.

"The JCS have always viewed SDI as a way to augment current U.S. strategy," in which deterrence against the threat of Soviet attack rests on the certainty of U.S. retaliation with nuclear weapons, the official said, "whereas Weinberger's office sees SDI as a path away from the current strategy," and toward a policy of deterrence based on defense against a Soviet attack.

Until now, the official said, the debate has remained unresolved because SDI had special status and was not forced to compete directly for funds with other, more traditional weapons programs.

Pentagon officials said that Abrahamson agreed to subject his program for the first time to the scrutiny of Defense Acquisition Board members from the Army, Navy, Air Force and the JCS in hopes that their approval would give the program new military and political prestige. Previously, the officials said, Abrahamson has complained that while other program officials had large coteries of senior military officers with them during congressional appearances, he had only the support of the agency's political appointees.

The board also is expected to approve a statement by the JCS attesting to the military need for a comprehensive strategic defense. Under Defense Department rules, no major weapons program can be created without one, although no such statement was ever drafted for SDI, according to Pentagon officials.

"Some kind of operational requirement, some statement of need" is always required before the Defense Department can "bend metal and . . . produce things," Lt. Gen. Harley A. Hughes, the Air Force deputy chief of staff for plans and operations, explained to an Air Force Association conference in Colorado Springs last month.

But SDI was "generated by the president," Hughes said, and so "we didn't have that operational requirement out front before the president's vision of a world of no-nukes which this contributes to."

Hughes, who also serves as deputy to the JCS for military operations, said they were "working very hard to come up with . . . {a requirement for SDI} that makes sense, is militarily significant, {and} is cost effective."

Several knowledgeable sources said the deliberations were highly contentious because some officials on the JCS believe the missile defense cannot be deployed before the late 1990s, and would be able to defend against only a limited or "accidental" Soviet attack involving the offensive missiles already in the Soviet arsenal.

New Soviet missiles that fly much more rapidly could penetrate the defense, these officials said, because U.S. space-based rockets could not reach them quickly enough.

During his Colorado Springs speech, first mentioned in the newsletter "Military Space," Hughes alluded to the widespread concern that the tab for Weinberger's deployment plan would be paid by cutting existing programs.

"I submit {that} the most dangerous period of time that we'll encounter in the next 20 years will be the period {in which} we begin to put a space defense system in orbit and it becomes effective," Hughes said. "To continue to deter {the Soviets}, it is obvious that we need to maintain the triad" of strategic missiles, bombers and submarines during this period.

As a result, SDI has "got to be funded independently of any other programs that we have," Hughes said, adding that "there is total agreement amongst the Joint Chiefs," senior military field commanders and senior staff members in the three military services on this point.

Several officials noted that the SDI program, for which $3.2 billion is budgeted this year, would require at least $10 billion annually over the next seven to 10 years if Weinberger's plan is to be carried out while other related research is continued. They said they doubted that Congress, which has been restricting the overall defense budget, would agree to take the additional funds from nonmilitary programs.

Over the past three years, these officials noted, SDI absorbed all of the additional funds Congress provided for research and development on strategic weapons, and under the proposed budget for fiscal 1988 the SDI office would spend almost as much as the Army spends on all of its research and development.

The officials also warned that more, not fewer, strategic weapons might be needed if Weinberger's deployment plan is approved. Gen. John T. Chain, head of the Strategic Air Command, said at the Colorado Springs conference, for example, that "with SDI we will have nailed the door shut and left the windows open."

Chain said "the point is that once we build a shield against the incoming missiles, then we have to worry . . . about bombers delivering gravity bombs, delivering standoff missiles, delivering cruise missiles, and submarines and ships delivering air-breathing cruise missiles," which could be stopped only with new U.S. weapons.

Chain also said that "if the Soviets build an SDI then that means I'm going to have to have a larger bomber force" to attack Soviet targets. He added, "The day that we end up with an SDI system on both sides . . . this country may have 1,000 {or} 2,000 bombers," and it will also "be big" in nuclear-armed cruise missiles. The United States has roughly 350 strategic bombers.

Others, such as Gen. Robert Herres, a former head of the U.S. Space Command who is now vice chairman of the JCS and the Defense Acquisition Board, are said to be more supportive of the missile defense deployment plan and enthusiastic about its ability to help defend against a surprise Soviet attack on vital military targets.