The Soviet Union warned America's NATO partners anew tonight to heed President Leonid Brezhnev's proposed freeze on new medium-range nuclear weapons in Europe or face worsening relations with the Kremlin.

An authoritative statement, scheduled to appear as a commentary in Saturday's edition of the Communist Party newspaper Pravda, was clearly designed to continue the diplomatic blitz that Brezhnev launched earlier this week with a series of private letters to West European leaders.

Given what the Soviets regard as disappointing official responses, the public drive is seen by political analysts as an effort to generate public pressure in Western Europe against the deployment of new weapons and thus block the Reagan administration's efforts to move closer to its NATO partners.

The Soviet statement asserted that the scheduled placement of U.S. intermediate-range nuclear missles "will qualitatively complicate" the military balance and "cannot but affect the Soviet Union's relations with each of the countries which will provide [their] territory for deployment of weapons threatening the U.S.S.R."

The warning was twinned with the argument that the deployment of new American missiles would make more difficult any future talks to limit nuclear arms in Europe.

The United States contends that the NATO decision to station 572 cruise and Pershing II missiles in Europe is intended to restore the balance that was upset when the Russians started deploying their modern SS20 missiles. With Moscow having about 160 of these missiles, which could reach targets as far as Britain, Western military exports contend that failure to deploy the new U.S. weapons would preserve Soviet military superiority in Europe.

The Soviets emphasized the commentary's importance by transmitting the full text tonight via the official Tass news agency. The author is Alexei Petrov, thought to be a pseudonym for making known views of the leadership.

It shows Soviet annoyance at the cool Western reception to Brezhnev's proposals, accusing Bonn and Washington of countering "with a formalistic proposal on negotiations though from the very beginning the U.S. did not conceal it [will] conduct them in a slipshod manner."

Pravda said any Western arms buildup "spearheaded against the national security of the Soviet Union and its allies" will be matched by Moscow. It added that if U.S. forward-based and other muclear strike forces were not present in Europe, "the Soviet Union would have no need to counterbalance these means. This is how the question is posed.This is known to every objective person."

Western diplomats have predicted that if Brezhnev's initiative were spurned, the Kremlin would mount a propaganda offensive, depicting itself as a socialist dove among capitalist hawks. Today's statement comes as NATO's special consultative group has scheduled a March 31 session on Brezhnev's arms control proposals. European press reports indicated NATO interest in general responses to the proposals before the May 1 NATO ministerial meeting in Rome.

Consistent with Soviet tactics on the issue for almost two years, the statement argues that Moscow has not achieved superiority in the European theater with its deployment of mobile SS20 missiles, but only answered NATO superiority in battlefield nuclear capability.

But the commentary is notable for its bluntness, for new criticism of President Reagan after a brief honeymoon, and new denunciations of West German Chancellor Helmut Schmidt for rejecting the Brezhnev initiative recently.

While Reagan is chided for "undiplomatic expressions," Pravda emphasized Kremlin expectations of a positive U.S. response to Brezhnev's call for resumption of bilateral dialogue "at all levels," by asking: "If points of contact between the positions of the sides have begun to appear, is it not more correct to start without delay discussing the substance of the issues?"

But, Pravda continued, "closer scrutiny" of Western promises of thorough study of disarmament proposals Brezhnev made Feb. 23 while suggesting a summit with Reagan shows that "some NATO members [instead] have in mind [formulating] a stand on the basis of earlier rearmament decisions."

It criticized West German Foreign Minister Hans-Dietrich Genscher, who after talks in Washington earlier this week said the NATO deployment plan must proceed as a condition for theater nuclear force talks with Moscow. Brezhnev has proposed a simultaneous freeze and talks, an idea he first raised before the December 1979 NATO decision to begin deployment by 1983.

Genscher is due here from April 2 to 4 for talks with Soviet Foreign Minister Andrei Gromyko.