President Yuri Andropov today belittled the Reagan administration's commitment to arms control in one of the sharpest attacks on U.S. foreign policy by a Soviet leader in recent years.

In a lengthy statement devoted entirely to U.S.-Soviet relations, Andropov accused Washington of pursuing a "militarist course" that raised the danger of nuclear war. He dismissed President Reagan's latest proposals on intermediate-range nuclear weapons in Europe and warned that the Soviet Union would respond to any attempt to disrupt the existing strategic balance.

Commenting for the first time on the shooting down of a South Korean airliner by the Soviet Union, Andropov blamed the United States for what he called "a sophisticated provocation, masterminded by U.S. special services" and "an example of extreme adventurism in politics." He said that Washington had exploited the furor surrounding the incident to step up the arms race.

Western diplomats who heard Andropov's statement, which was read by an announcer as the lead item on state television news, expressed surprise at the virulence of his language and the bleakness with which he depicted the current state of international relations. They said he appeared to be mounting a counteroffensive following a series of attacks by President Reagan and senior U.S. officials on the Soviet Union.

While Soviet rhetoric against the United States has reflected the deterioration in relations between the superpowers during the past few years, diplomatic observers here could recall few precedents for the sweeping nature of Andropov's attacks. The Soviet leader seemed to rule out all hope of any breakthrough in the Geneva talks on intermediate nuclear weapons on the basis of present U.S. proposals.

In Washington, a State Department statement said, "The world will be deeply disappointed with the Andropov statement. He has for the first time associated the highest levels of the Soviet government with the pathetic charge that the Soviet shootdown of the civilian aircraft was the result of 'a sophisticated provocation, organized by the U.S. special services.' The international community expects and awaits a different answer . . . .

"The world will be disappointed that Mr. Andropov's response to the president's major arms control initiative at the United Nations is a threatening restatement of their long-standing position that the Soviets will maintain their monopoly of intermediate-range missiles in Europe. For our part, we will continue to work in Geneva for a negotiated settlement that strengthens international peace and security."

Andropov lashed into past and present U.S. policies around the world--from Central America to Lebanon to what he depicted as attempts to stir up militarism in Japan. On arms control, he said the United States was unwilling "to conduct serious talks of any kind" and was simply playing for time at negotiations in Geneva on intermediate-range nuclear weapons and the parallel talks on long-range, or strategic, missiles.

Andropov also questioned the suitability of the United States to act as the host for the United Nations and warned Western European leaders that they were being used as political "hostages."

One of the main messages in the 3,000-word statement was that the Kremlin would show no weakness in the face of threats from abroad. Andropov said that people who had attempted to undermine the Soviet Union's independence or Communist system in the past had ended up on "the garbage heap of history."

"The Soviet people can rest assured that our country's defense capability is maintained at such a level that it would not be advisable to anyone to stage a trial of strength," he said.

Publication of the statement was an unusual way of making the Soviet leader's views known. A Soviet official said today that Andropov, who has not been seen in public since late August, has still not returned to Moscow from his vacation.

The statement, which was couched in grave and somber terms, began with the words: "The Soviet leadership deems it necessary to make known to the Soviet people, other peoples, and all those who are responsible for shaping the policy of states its assessment of the course pursued in international affairs by the present U.S. administration.

"To speak briefly, this is a militarist course which poses a grave threat to peace. Its essence is to try and assure for the United States domineering positions in the world without reckoning with the interests of other states and peoples."

Andropov said that the past two years of talks in Geneva had proved that U.S. negotiators were not ready to reach an agreement.

"Their task is different--to play for time and then start the deployment in Western Europe of ballistic Pershing II and long-range cruise missiles. They do not even try to conceal this. All they do is prattle about some flexibility of the United States," he said.

Dismissing Reagan's latest arms proposals, Andropov said: "We are being asked to talk on how to help the NATO bloc to upset to its advantage the balance of medium-range nuclear systems in the European zone. And this move is presented brazen-facedly as something new."

He did not deal with the details of Reagan's offer to include nuclear bombers in calculations of medium-range weapons systems or to refrain from matching global levels of Soviet warheads.

Describing U.S. policies as short-sighted, cynical and suicidal, the Soviet leader expressed surprise that Western European politicians were going along with Washington's determination to deploy new U.S. nuclear weapons in Europe. He accused the European leaders of "disregarding the interests of their peoples and the interests of peace" by helping to "implement the ambitious militarist plans of the U.S. administration."

Adding that the Americans had shown no sign of being willing to do business at the strategic arms talks, Andropov said the United States was planning to launch the production of new "weapons which may radically alter the notions of strategic stability and the very possibility of effective limitation and reduction of nuclear arms."

"No one should mistake the Soviet Union's good will and desire to come to agreement as a sign of weakness. The Soviet Union will be able to make a proper response to any attempt to disrupt the existing military-strategic balance, and its words and deeds will not be at variance," he said.

Claiming that U.S. leaders had shown contempt for the United Nations, Andropov asked: "Can the international organization, called upon to maintain peace and security, remain in the country where outrageous militarist psychosis is imposed and the good name of the organization is insulted?" The Kremlin has accused the United States of making it impossible for Foreign Minister Andrei Gromyko to attend the present session of the U.N. General Assembly in New York.

Saying that the Reagan administration was waging a crusade against communism, Andropov attacked the "transference of ideological contradictions to the sphere of inter-state relations."

"This is simply absurd and inadmissable at present in the nuclear age. Transformation of the battle of ideas into military confrontation would be too costly for the whole of mankind," he said.