The Soviet Union and its Warsaw Pact allies advanced a series of sweeping disarmament proposals today, calling the package "an alternative to nuclear catastrophe."

The Soviet Bloc leaders released details of the proposals announced yesterday at the end of a two-day summit meeting in Prague, including an offer to sign a nonaggression treaty with NATO in which both sides would pledge not to be the first to use any kind of military force--conventional or nuclear.

The document also renewed virtually all Soviet arms control proposals made in recent years and reaffirmed Moscow's strategic doctrine that "there can be no winners in a nuclear war once it breaks out."

But the 7,000-word document placed sharpest focus on Western Europe in a clear and fresh effort to mobilize western support against the planned deployment of new medium-range nuclear missiles in five countries of the North Atlantic Treaty Organization.

The tone of the document was moderate and reasonable and appeared designed to impress western Europeans with the sincerity of the Soviet Bloc's peaceful intentions. Several of the measures proposed, in particular the nonaggression treaty, were seen by diplomatic analysts as aimed at West Germany, where national elections are to be held in March.

According to these analysts, West Germans have showed interest in the nonaggression proposal in the past.

The proposals appeared to include some new elements, giving a higher and more explicit priority than previous Warsaw Pact policy pronouncements to military confidence-building measures and the verification of arms control agreements.

The communique formalized for the first time a specific commitment to international verification of such agreements, saying that proper verification measures should include "when necessary, international procedures."

Although the Soviets have shown signs of flexibility on this issue during the past year, today's specific reference to "international procedures" was seen by analysts as a significant shift away from traditional Soviet insistence that arms accords should be verified only by the so-called "national technical means"--a euphemism for spy satellites and other electronic intelligence-gathering facilities.

The question of verification has been one of the major arguments advanced by western opponents of arms control, who have argued for some form of on-site inspection by foreign specialists or by automatic devices monitored by foreign specialists.

Foreign Minister Andrei Gromyko said last year that Moscow would be prepared to accept on-site inspection "on an agreed basis" for chemical weapons if the West was prepared to sign a convention banning such weapons.

In addition to offering to negotiate a nonaggression pact, the communique proposed a "practical agreement" with NATO on "nonescalating military spending" and later negotiating reductions in arms outlays.

Calling the planned deployment of new U.S. missiles "the most serious threat posed to the European nations," the Prague declaration proposed a radical reduction of all medium-range nuclear weapons in Europe along the lines put forward by Soviet leader Yuri Andropov.

It said the Soviet-U.S. arms negotiations in Geneva have an "artificial deadline" set by the fact that NATO intends to begin deployment of the 572 U.S. Pershing II and cruise missiles by the end of this year if the talks do not produce an agreement.

In an indirect criticism of the Reagan administration, the document said that those who seek to deploy these weapons can merely "continue to procrastinate" in order "to use the lack of agreement as a pretext to begin the actual deployment."

"In view of the vital importance of the reduction and limitation of medium-range nuclear weapons in Europe for all the European peoples," the document said, "the participants in the meeting expressed the hope that all European states will contribute to the progress at the Soviet-American talks on this issue and to their successful conclusion."

In proposing a nonaggression pact to NATO, the Warsaw Pact said it was not seeking military superiority and that it had no intention of attacking any NATO country. Since NATO professes the same positions, the document said, "there should be no reason preventing the adoption by the states comprising the two alliances of mutual commitments of an international legal character."

The proposed joint pledge not to use force would apply to all military and civilian personnel, ships, aircraft and spacecraft wherever they may be located. It would also involve the pledge to avoid the use of force against other countries and to preclude threats to international air, sea and space communications.

The Soviet Bloc proposed to seek "practical" measures to prevent a surprise attack and to promote military, air and naval exchanges in order to strengthen confidence between the two blocs.

An exception to the treaty would be the use of force in self-defense under the U.N. Charter, the provision used by Moscow when it sent troops to Afghanistan in 1979.

The Warsaw Pact document, distributed by the official Soviet news agency Tass, said the proposed pact would be open to other countries in Europe and elsewhere to sign.

It also urged a variety of other negotiations, asserting that the Soviet Bloc is prepared to remove all chemical weapons from Europe and make a major effort to get the 10-year-old Vienna talks on force reductions in Central Europe off dead center.

While calling for reductions in Soviet and U.S. forces in Central Europe, the Prague declaration made no specific proposals to suggest a shift in the Warsaw Pact position on the Vienna talks.

The leaders of the Soviet Union, Bulgaria, Romania, Czechoslovakia, East Germany, Poland and Hungary also reaffirmed their commitment to the 1975 Helsinki agreement on security and cooperation in Europe and touched on economic and cultural matters.

The document emphasized the importance of "truthful information" and, in an apparent reference to the West German-based American stations, Radio Liberty and Radio Free Europe, complained about the dissemination of "downright slanderous news" and said that "no state should allow such subversive activities to be conducted from its territory."

Despite the provisions in the Helsinki accords calling on all signatories to facilitate such visits by foreign reporters, Czechoslovakia has refused to issue visas to a number of western journalists who planned to cover the two-day Prague summit.

The Prague declaration also called for a treaty on complete and universal prohibition of nuclear weapons tests, prohibition and elimination of chemical weapons, a convention to ban neutron bombs, talks on prohibiting any type of weapons in outer space and a ban on radiological weapons.

It said it was "necessary" to make "fresh efforts" to substantially reduce levels of conventional arms and to resume talks on limiting their sales.

"The arms race is evolving into a qualitatively new and far more dangerous phase" involving both nuclear and conventional weapons, the document said. It held the Reagan administration chiefly responsible for increasing tensions in which "the threat of war, primarily nuclear war, is growing."

But it said that the present course "can be stopped and redirected" and that its proposals constitute "an alternative to nuclear catastrophe and call for large-scale international cooperation to preserve civilization and life on earth."

It continued: "It is necessary to act without delay, while there is still a possibility to curb the arms race."