The Senate Foreign Relations Committee yesterday gave unanimous approval to a declaration proposed by George McGovern (D-S.D.) stating the Senate's intention to to approve any future SALT agreements that fail to provide for substantial reductions of the superpower's nuclear weapons.

Approval of the McGovern proposal as a declaration to accompany the resolution of ratification for SALT treaty reaches the floor.

The McGovern declaration begins with an expression of senatorial "disappointment" that strategic arms control negotiations until now "have failed to achieve" quantitative reductions or more significant qualitative limit on nuclear arnaments.

This disappointment is widely shared in the Senate, by doves like McGovern and hawks at the other end of the spectrum as well. The most hard-line senator on Foreign Relations, Jesse Helms (R-N.C.), voted with McGovern in the committee yesterday.

The Carter administration says it can accept McGovern's proposal, but is much less willing to entertain stronger measures along the same lines that may be introduced on the floor. The administration is reluctant to let the Senate dictate the terms of future SALT agreements as a condition for approving the pending one.

But several senators whose votes on SALT II may be crucial insist that the Senate must go further than the McGovern declaration to satisfy them. Included in this group are Mark O. Hatfield (R.Ore), Howard M. Metzenbaum (D-Ohio) and Daniel Patrick Moynihan (D-N.Y.), and perhaps several more.

Moynihan already has proposed a much stronger amendment to the SALT II treaty that would require the Soviet Union and the United States to negotiate a SALT III agreement that includes substantial arms reductions by the end of 1981, or else the SALT II treaty would lapse at that time.

Moynihan has indicated a willingness to negotiate on the details of his plan, but insists that at the very least the Senate should set some kind of deadline for the successful negotiations of significant arms reductions.

Sen. Alan Cranstn (D-Calif.), the majority whip, has been working with Moynihan, and said last night he thought the New York Democrat would accept a proposal to allow the Senate to vote on continuing or abrogating SALT II at a future time if there had been no new Soviet-American agreement on arms reductions. An aide to Moynihan said he had not yet accepted this sort of compromise.

Cranston said last night he believed it would be necessary to go "a little farther" than the McGovern declaration to satisfy senators who have been most concerned about arms reductions.

McGovern's proposal would not be legally binding, since this Senate can not commit future Senates on SALT issues. It would be similar to Senate declarations passed at the time of SALT I. One of them had an apparent impact on the SALT II negotiations, but two -- as Moynihan pointed out on the Senate floor -- had no effect.

The one that had some impact was sponsored by Henry M. Jackson (D-Wash.). It said SALT II should provide for U.S. strategic nuclear forces not inferior to those of the Soviet Union (SALT I had granted the Soviets more weapons in some categories). Jackson claims his declaration wasn't satisfied fully; others say it was by the equal arms ceilings in SALT II.

Moynihan noted that two other declarations passed with SALT I, calling for arms reduction talks and calling on both superpowers not to acquire weapons that could destroy the others' missiles in their silos, were both ignored.

The McGovern proposal adopted unanimously by the Foreign Relations Committee asks for "significant and substantial" arms reductions. In a speech, McGovern said this should mean cuts of 25 to 30 percent of the arms levels permitted by SALT II. The declaration urges the president to negotiate "continuous year-by-year reductions" in the levels allowed by SALT III. McGovern said 5 to 10 percent a year would be a good rate of reduction.