The Soviet Union has been pursuing an "enormously expensive" program of constructing huge underground bunkers and subways to protect its leaders and allow them to fight a protracted nuclear war, Defense Secretary Frank C. Carlucci said Friday.

While the existence of such complexes has been known for years, "only recently have we been able to do the full analysis of the enormous extent of this program hundreds of meters deep, with subways under several cities," Carlucci added."To have something comparable, we'd have to have facilities where we could put every governor, mayor, every Cabinet official and our whole command structure underground with subways running here and there. There's just no comparison (with U.S. shelters built in the 1950s)."

Carlucci highlighted the Soviet Union's so-called passive defense program as he released the 1988 version of "Soviet Military Power," an unclassified study of what the Russian military has been doing over the past year.

The defense secretary cited the underground work as just one example of how Soviet actions paint a different picture than the public statements of Kremlin leader Mikhail S. Gorbachev, with his emphasis on arms control initiatives and improving the economy.

Without elaborating, Carlucci also made it clear the United States was developing a means of threatening the underground bunkers.

"Although the (Soviet) program strikes at the very basis of deterrence, we have a number of initiatives underway that will provide us an effective response to this program at a fraction of the cost that it must have taken the Soviets to undertake it," he said.

Last year, Defense and Energy Department officials acknowledged work had begun on a new family of "earth-penetrating" nuclear warheads for U.S. missiles.

"There can be only one purpose for these shelters to provide the Soviet leadership the ability to fight a protracted nuclear conflict," Carlucci declared. "These facilities contradict in steel and concrete Soviet protestations that they share President Reagan's view that nuclear war can never be won and must never be fought."

The 1988 review, the last to be prepared by the Reagan administration, is the seventh such assessment of Soviet forces. This year's 175-page glossy publication differs substantially from the earlier reports, though, in that it tries harder to gauge who's leading whom in various technologies and regions of the world.

The report does still focus on some new weapon developments, though. Among them:

The Soviets will soon deploy operational units of their new Blackjack long-range bomber. Deployment of the new rail-mounted SS-24 nuclear missile has begun, and production should start soon for a more accurate version of the huge SS-18 intercontinental ballistic missile.

Carlucci said the deployment of the SS-24 was significant, because it means the Soviets now have two operational ICBM's that are mobile "while we're still arguing in the Congress about whether we should have one . . ."

Two new attack helicopters, the Havoc and Hokum, "are expected to enter serial production soon," and the Soviets have begun fielding "a new tank derived from the T-72, exhibiting improved protection, better mobility and enhanced firepower."

"The Soviets are on the verge of deploying a variety of sophisticated cruise missile systems," and continue to lead the West in the pace of their activities in outer space.

In the area of Star Wars, the Soviets like the United States are unlikely to develop small "kinetic kill" rockets that could be placed in space to shoot down nuclear missiles at long range. The Soviets could, however, "deploy a short-range, space-based system for space station defense or close-in attack by a maneuvering satellite in the near future."

In Europe, the Soviets continue to improve their already large advantage in conventional weapons and troops. But the North Atlantic Treaty Organization is strong enough to deter attack primarily because the Soviets believe the Western allies would resort to nuclear weapons if in danger of being overrun, the Pentagon said.

That ability to deter an attack may depend, however, upon success in developing new types of conventional weapons "and the West's current technological lead is threatened by an extensive Soviet commitment to surpass the United States and its allies."

The Soviet news agency Tass, in a response written by Washington correspondent Oleg Polyakovsky, criticized the administration Friday for continuing to publish the Pentagon review.

"The stirring up of the myth about the Soviet military menace is a traditional method of the U.S. politics, particularly at a time when the budget is being drafted," Polyakovsky said. "Such a publication can do nothing but harm to Soviet-American relations."

One interesting section of the report said there "are major causes for concern" over the "secrecy" surrounding the building of a system of underground tunnels beneath Moscow and other major cities designed to assure the survival of Soviet leaders during a nuclear war.

Such construction has been under way for the last 40 years, the Pentagon said, but a new round was started in the early 1980s.

Carlucci said that intelligence agencies only recently were able to do "a full analysis of the enormous extent" of the tunnel system. "So, this is the first that we've been able to describe it in detail."

The Pentagon has a number of weapons programs under way "that will provide us with an effective response (to the tunnels)," Carlucci said. He declined to say if they were new earth-penetrating nuclear warheads.

The report is primarily the work of the Pentagon's Defense Intelligence Agency in conjunction with other government agencies.