The retiring chairman of the Senate Foreign Relations Committee says Americans may have overrated the Soviet Union's strengths and, consequently, demanded tougher policies than necessary toward Moscow.

Sen. John J. Sparkman (D-Ala.) said the Soviet Union, while "exceptionally strong" as a military power, economically and socially exhibits "many of the characteristics of a developing country."

Many Americans have seen the Soviet Union only as a military power and "have demanded of one president after another that the United States be prepared militarily to 'stand up' to the Soviets," he said.

"With a more accurate perception of the Soviet Union, Americans may demand of their presidents that they be as willing to 'sit down' with the Russians as they have been to 'stand up' to them," said Sparkman, who is ending a 42-year career on Capitol Hill.

Sparkman's comments appeared in the introduction to a book, "Perceptions: Relations Between the United States and the Soviet Union," published yesterday by his committee. The book consists of 80 essays by experts and scholars, including former secretary of state Dean Rusk and Sparkman's predecessor as chairman, former senator J. William Fulbright (D-Ark.).

The book covers a wide range of subjects, including the military and economic relationships between the Soviet Union and the United States, Western Europe and the communist nations of Eastern Europe.

Fulbright, now associated with a Washington law firm, said he believes U.S. policy toward Moscow may have puzzied the Soviets even more than their closed society has baffled U.S. policymakers.

He noted that U.S. policy has been influenced by various factors, including tough Cold War policies, communist-hunting activities, political pressures for higher defense spending and the moves toward detente.

By contrast, the Soviets' policy statements over the years have consistently focused on "peaceful coexistence and detente," Fulbright said.

Rusk said there has been too much conflict and too little consultation between the administrations and Congress in the formulation of U.S. foreign policy.