Arkady Shevchenko, the high ranking Soviet official at the United Nations who recently defected from his country, is seeking political asylum in the United States, it was disclosed here yesterday.

The 47-year-old career diplomat contacted State Department and Immigration and Naturalization Service officials through his New York lawyer before he announced yesterday that he intended to take "the necessary legal steps to establish residence in the United States."

"You can safely assume that he is welcome to stay," State Department spokesman Tom Reston said last night in response to questions whether Chevchenko's reques would be granted.

U.S. officials, however, were exceptionally reluctant to discuss the case, which involves the highest ranking Soviet official ever to defect to the West. Privately, they said the Shevchenko would be granted asylum irrespective of his decision whether or not to cooperate with U.S. intelligence officials.

Shevchenko, in a carefully worded statement issued yesterday, said his decision to remain in the United States was prompted by "serious differences of political philosophy and conviction with the present Soviet system."

It was issued shortly after the United Nations announced that Shevchenko had quit his $76,000-a-year job as U.N. undersecretary general for political and security affairs, effective yesterday.

Shevchenko will receive more than $76,000 in severance pay under an agreement he reached with U.N. Secretary General Kurt Waldheim during their hour-long private meeting Tuesday night.

By terminating his association with the United Nations, Shevchenko automatically lost the diplomatic status under which he was allowed to reside in the United States. His lawyer, Ernest Gross, said in a telephone interview that Shevchenko was now seeking to obtain "alien resident status."

Several categories under which this could be done include a special ruling by the Justice Department, political asylum, and granting of a status under which stateless persons are permitted to live in the United States. The rationale in all these categories is that the applicant, if he were to be returned to his native country, would face persecution for his political views and actions.

Shevchenko's statement about his "serious differences" with the Soviet system, as well as his defection itself, were believed to provide sufficient grounds for favorable U.S. response to his asylum request.

In his statement, Shevchenko also made it clear that he wanted to avoid public discussion of his political views "at this time" because that "would not be helpful to Soviet-United States relations or to my family in the Soviet Union."

Shevchenko, who spent 12 of the past 15 years at the United Nations, has earned a reputation as an arms control specialist. He was the youngest Soviet diplomat to achieve the rank of ambassador when he became special adviser to Foreign Minister Amdrei Gromyko in 1971.

Since 1973 he had held the highest post allowed to the Soviet Union under the U.N. system and one of his latest official photographs distributed by the United Nations shows him sitting next to Soviet President Leonid Brezhnev during Brezhnev's talks with Waldheim last fall.

Shevchenko's wife flew home to Moscow on April 9, one day before it was disclosed that he had refused to return home. The Shevchenkos have a teenage daughter and a diplomat son, both in Moscow.

The Soviet Union has charged that Shevchenko was being held "under duress" by U.S. agents, but Shevchenko met twice with senior Soviet diplomats in his lawyer's office to confirm that he was acting of his own free will.

Gross said yesterday that one of the principal subjects of discussion dusing those two meetings was Shevchenko's effort to gain "certain assurances from the Soviet government regarding his family" in Moscow. Shevchenko also too steps to transfer the title to his cooperative apartment in Moscow and his country dacha to his family and sought assurances that he would be allowed to send money to his wife.

"These discussions are still under way," Gross said.

Since his defection, there were reports that Shevchenko had been in touch with CIA and FBI agents for several years. These reports have not been officially confirmed.

U.S. officials here said yesterday that Shevchenko had been in touch with FBI officials recently, but these contacts were made in connection with his efforts to gain permanent residence in the United States.