Led by the Army's Ballistic Missile Defense Agency (BMDA), the Reagan administration is beginning to look at how the 1972 anti-ballistic missile treaty with the Soviet Union might be modified to permit protection of strategic command and control centers and, possibly, new land-based MX intercontinental ballistic missiles.

Defense Secretary Caspar W. Weinberger said he has not made up his mind which of the several MX basing plans -- placing the missiles aboard airplanes, shuttling them among shelters or putting them in existing silo -- to recommend to the president and Congress.

The latter course, proposed as one solution by the Weinberger-appointed Townes Commission, calls for putting 100 of them in silos that now hold Titan and Minuteman missiles, and defending those silos with a new mobile anti-ballistic missile system that is in advanced research.

Using a concept called "preferential defense," the mobile ABMs would defend some but not all of the silo-based MX missiles. But because the Soviets would not know which silos were being defended, they would have to fire many warheads at each one.

If this approach, which has been discussed with Weinberger, is accepted by him and the president it would require a modification of the 1972 treaty, since even testing of mobile ABM components is barred by the pact.

The Reagan Pentagon was warned by departing Carter administration officials that any attempt to abrogate the ABM treaty would be met with stiff resistance, not only by elements within Congress and in the public at large, but also by U.S. allies in Europe who have been pressing for more rather than less arms control talk.

For that reason, according to one Reagan defense official, any attempt to modify the ABM treaty will be couched in arms control terms. A return of ABMs, he said, "would be done for stability purposes, to permit both sides to defend a smaller force of ICBMs and thus not need to put more dollars and rubles into additional missiles."

One measure of how seriously Weinberger considers ABMs is his decision to devote one of three Defense Science Board (DSB) meetings this summer to a study of "what kind of ABM we could have by the mid or late 1980s," according to a Pentagon official involved in the process.

The DSB, which will meet the first two weeks in August, will look at the technologies developed by the Army's BMDA, as well as a new approach being pushed in the Pentagon to use a Navy Aegis early warning radar system with the Sprint ABM missile that was originally developed for the now-discarded Safeguard ABM system.

Under terms of the ABM treaty, the United States and the Soviet Union are scheduled to sit down sometime late next year for a regularly scheduled five-year review of how the agreement is operating.

The last review, in 1977, under the newly elected Carter administration, was recently described as "perfunctory" by several civilian and military men who participated in it.

But Reagan defense strategists and their conservative allies in Congress have been pressing for a serious review of the treaty that would pave the way for an expansion of the one ABM site with 100 missiles allowed under its terms.

A top Pentagon official said last week that he expects to order studies on possible treaty modifications shortly, but is delaying that action until the president announces his decisions on deployment of the MX missile.

A key Reagan defense official, however, said both the Pentagon and the Arms Control and Disarmament Agency have studies under way on various aspects of the ABM treaty and how they could be modified.

In March, the BMDA awarded a $224,000 contract to Science Applications Inc., a Virginia-based think-tank, that has offices in Huntsville, Ala., home of the Army ABM command. The contract calls for a "qualitative and quantitative analysis" that would prepare the Army agency for recommending positions to be taken on the ABM treaty, according to a spokesman for BMDA.

According to one defense consultant who was among those bidding on the BMDA contract, "The Army agency expects to be called on to play a staff role in the 1982 treaty review and wants to have facts available to present on what portions of the treaty the U.S. should protect, and which ones would be advantageous for us to change."

As an example, he said it was clear that the BMDA thought there was "no advantage to the U.S. to cease the treaty in 1982, since the agency thought the Soviets were closer to a workable system than we were."

On the other had, he said, "to be able to test and evaluate mobile ABM components would be in our interest."

The BMDA has been receiving an average of $200 million a year for ABM research during the nine-year life of the treaty. Initially, after the treaty first went into effect, there was little public support for resurrecting ABMs.

But over the past few years, as concern grew over the possible vulnerability of the U.S. land-based missiles to a first strike from the Soviet Union, there was a rebirth of interest in ABMs. For its part, the BMDA has recently sponsored a series of seminars aimed at developing a new intellectual base for ABMs.

Six such seminars have been conducted in Washington since 1978, attracting officials from the Pentagon and State Department, consultants from a variety of defense think-tanks and aides to key senators and members of Congress who deal with the defense budget.

"The seminars have had a definite pro-ABM slant," according to a Capitol Hill aide who has attended more than one of them. As one defense consultant put it, "'Til now there has been a slow and steady drumbeat for ABM, how great the technology has become and that the treaty has to be reviewed in 1982."

One of the BMDA seminars, held at the Madison Hotel in Washington on Sept. 18-19, 1979, was titled "The Future of U.S. Land-Based Strategic Forces." The 60 or so participants were treated to a series of conservative defense speakers on the U.S. and Soviet forces and concluding with a presentation on "BMD's role in national survival, a first assessment."

The speaker was Ellory Block of Science Applications Inc., the same man who now will play a key role in BMDA's new contract with SAI on what to recommend on the ABM treaty.