There is little public awareness that the president, on his own, has the power to "turn a conventional war abroad into a nuclear war," the Federation of American Scientists has declared in launching a campaign to put "an additional lock" on the nuclear trigger.

Most Americans do not know that the president can use nuclear weapons against a Soviet attack with conventional weapons, according to a recent survey by the Public Agenda Foundation, a non-partisan research organization headed by pollster Daniel Yankelovich. It showed that four out of five Americans erroneously believe that it is U.S. policy to launch nuclear weapons "only if" the Soviet Union fires first.

The scientists' federation announced a year-long campaign to explore, explain and challenge a president's ability "on his own initiative" to escalate a conventional war into a nuclear conflict.

It is not the president's right to respond with nuclear weapons to a Soviet nuclear attack that is disputed by the federation, but rather "unfettered" authority for "first use" of the weapons. It is a staple of NATO strategy that a president can begin a nuclear confict "that might destroy our nation" without a declaration of war, or any discussion with Congress, said Jeremy J. Stone, director of the scientists' federation.

This process is both "unconstitutional" and "unwise," Stone said last week at a news conference sponsored by Foreign Policy magazine. To draw Congress into the decision-making process, the federation proposes a "special nuclear planning committee" that would give Congress "a veto over first use of nuclear weapons." This committee could secretly confer with the president to preserve the effectiveness of the nuclear deterrent.

"We do not agree," the Department of Defense countered, in a letter from General Counsel Chapman B. Cox, written on behalf of Defense Secretary Caspar W. Weinberger and released by Stone. Cox was responding to an article by Stone in the current issue of Foreign Policy, entitled, "Presidential First Use Is Unlawful."

"To ensure that the flexible response policy" of NATO "actually deters," Cox said, "a potential aggressor must be convinced that NATO is indeed ready to use any of the weapons it possesses, including, if necessary, nuclear weapons."

Cox continued, "Your call for an additional procedural requirement that would have to be met before a decision could be made for first use of nuclear weapons would threaten NATO's ability to deter Soviet aggression. Thus, it would tend to undermine NATO's deterrence policy."

In recent years, some leading policy-makers in earlier administrations, including Robert S. McNamara, McGeorge Bundy and Henry A. Kissinger, have said that NATO strategy for "first use" of nuclear weapons in Europe is no longer credible against a Soviet conventional attack. They have urged, instead, strengthening allied conventional forces.

The scientists' new challenge says that, in any event, the president should not be permitted to apply that strategy on his own.

Stone said the Cox letter "absolutely turns on its head" the assurances given Congress by Secretary of State Dean Acheson when the NATO treaty was ratified in 1949. Acheson said the treaty "does not mean that the United States would automatically be at war" if a NATO nation is attacked, because "Congress alone has the power to declare war" and such a decision "would, of course, be taken in accordance with our constitutional procedures."

Constitutional scholar Raoul Berger said at the news conference that the authority "to repel attacks" does not give the president any blanket authority to conduct war. It is "an extraordinary interpretation," Berger said, "that once we have been fired upon, Congress just becomes a wooden Indian" with "no further participation" in a war.