West German Chancellor Helmut Schmidt today underscored his support for the strategic arms limitation treaty (SALT), warning the Senate to approve it or risk "an even fiercer arms race" that could shatter the fragile balance of power between East and West in the coming "decade of unrest."

Speaking at Harvard's 328th commencement exercises, a traditionally prestigious foreign policy platform, Schmidt prefaced his comments by saying, "It is not my intention to interfere with the U.S. Senate's oncoming decision on ratifying SALT II."

But he quickly added that the treaty, which is expected to spark heavy debate in the Senate, is "not only a domestic matter for the American nation. This treaty is also a piece of world security and a piece of my own country's security."

Schmidt, on an unofficial five-day tour of the United States, labeled SALT "a prerequisite for the military and political stabilization of the East-West relationship and . . . a decisive factor in military and political detente."

Schmidt, speaking before an estimated 20,000 people in Harvard Yard, was booed when he declared his continued support for nuclear power, including an "option" for fast breeder reactors.

However, the crowd applauded his call for worldwide cooperation through the International Atomic Energy Agency in Vienna in developing safer methods of using nuclear power peacefully.

In his speech, Schmidt, who was accepting an honorary doctor of law degree, said, "failure of SALT II would be a setback for detente and a serious setback for ongoing arms control efforts. Instead of the universally sought curbing of the nuclear arms race, we would have to expect an even fiercer arms race.

"A failure of SALT II would also be a signal to the East. It would weaken the political elements there who are in favour of reconciliation and understanding with us in the West."

He added that West Germany, this country's principal NATO ally, faces increased jeopardy as the Soviet Union's arms stockpile grows.

"In Europe, no nation would be more seriously affected by the consequences of the failure of SALT II than the German nation," he said.

In response to SALT II critics, Schmidt noted, "We have to live with the paradox: we cannot trust in the communist ideology and its political aims, but we can and must endeavor to make use of the interest which communist leaders clearly do have in preserving peace and in dependability of treaties which they conclude."