A Central Intelligence Agency forecast that the Soviet Union will compete with Western nations as importers of Middle Eastern oil in the 1980s is incorrect, according to a Library of Congress energy study.

"Soviet needs and planned commitments require it to be a modest exporter on oil and natural gas to the hard currency Western industrilized nations and to Easter Europe throughout the period of the seventies and eighties, the study says.

A declassified CIA study forecasting that the Soviets and Eastern European bloc countries would import 3.5 million barrels a day by 1985 was released by President Carter the day he told the American people that his enenrgy plan was " the moral equivalent of war."

The CIA report, based on U.S. oil industry studies, was released at the urging of James R. Schlesinger Jr., the President's energy adviser, amid speculation that the administration was trying to generate a crisis atmosphere as the President unveiled his energy plan. Schlesinger headed the CIA during the Nixon administration.

The Library of Congress study was made by a team headed by DR. Herman T. Franssen. Undertaken months before the CIA study was released, it says the Soviets must continue to export oil and natural gas to earn the money to pay for Western imports and economic expansion.

The study estimates that by 1980 the Soviets will export about 256 million barrels of oil a year and 26 billion cubic feet of gas to Western Europe.

A copy of the study, which is expected to be released early next week, was obtained by The Washington Post from congressional sources.

Both the Soviet Union and the People's Republic of China "are not expected to be major exporters or importers of oil in the period ending in 1990," the study concludes.

Last year the Soviet Union led world oil production, pumping 10.4 million barrels - over 1 million barrels a day more than Saudi Arabia. According to Soviet trade figures, the Russians sold more than half of their oil exports to Western countries in 1976 in pursuit of "hard currencies." In the past, Soviet oil exports have been directed in large measure to meeting the oil needs of the Communist bloc countries, from Eastern Europe to Cuba.

Since world oil prices quadrupled in 1973, the Soviets have used oil to earn foreign exchange to offset balance-of-payments deficits and mounting debt to Western nations, now calculated at over $11 billion.

The Library of Congress study cites Soviet energy objectives over the next 15 years are:

Maintaining self-sufficiency in energy to meet domestic needs;

Servicing East European bloc needs;

Utilizing oil and natural gas exports to finance trade with Western industralized countries.

Last year the Soviets imported 150,000 barrels of oil a day, much of it from Iraq. Should the Soviets have to increase imports, analysts say they will probably turn to Iraq and Libya, two oil-exporting countries with political links to Moscow. Iraq's largest trading partner is the Soviet Union.

Last year U.S.-Soviet trade totaled nearly $2.6 billion, of which $1.4 billion went toward agricultural products.Without the foreign exchange earned by energy exports, the Library of Congress analysts argue, the Soviet would be unable to purchase vital foodstuffs and industrial, agricultural and consumer goods from the West.

The study suggest that Soviet oil production could begin to taper off in the 1980s, unless the Russians are able to develop potential resources in Siberia.

Asked about the accuracy of the CIA study, a senior State Department official said, yesterday. "The basis of the CIA study is really an engineering analysts, and the slowness with which new fields are developed . . . we found the CIA conclusions generally right."

"Any time you deal with a society that secretive you are never really sure," he said.