In a major address on arms control and foreign policy that echoed President Carter's Georgia Tech address of yesterday, Sen. Edward M. Kennedy (D-Mass.) gave a ringing, unreserved endorsement of a new strategic arms pact with the Soviet Union.

Political matchmakers could not have improved on the timing of Kennedy's speech, which followed President Carter's by barely two hours. the Massachusetts Democrat, Carter's principal rival but also one of his strongest supporters in the Democratic Party, made his remarks to the Arms Control Association here.

Kennedy gave a more forceful and detailed defense of the new Strategic Arms Limitation Treaty (SALT) than Carter did and took a few pokes at the Carter administration, but also quoted approvingly from the president's Georgia Tech speech and endorsed the main lines of his policy.

Kennedy attacked Henry Kissinger by name, challenging the former secretary of state's recent, critical remarks about SALT II as "not credible." Kennedy assailed partisanship in foreign policy generally, accusing "partisan voices" of selling America short by exaggerating U.S. weaknesses while ignoring American strengths.

Kennedy's criticisms of the Carter administration were less pointed, but clear enough. First, he called 1978 a "year of postponement" in the arms control field, and said "important opportunities may have been lost" because negotiations could not be brought to successful conclusions.

Later in the speech Kennedy charged that "arms control advocates and supporters" -- presumably including the president and his associates -- "are timid and defensive, where they should be confident and assured."

Kennedy's own defense of SALT II was anything but timid.

He extolled the agreement -- most of whose principal elements are now known -- without any reservations, while adding that it would be a mistake to expect SALT II to be a panacea.

Kennedy described the new agreements as "a small but essential step toward more effective nuclear arms control" that could save the United States as much as $100 billion -- the cost of "an unrestrained new round of the arms race," Kennedy said.

He ridiculed the idea that Senate approval of SALT should be "linked" to more acceptable Soviet behavior in other areas:

"Let the advocates of linkage explain how the cause of human rights a Senate refusal to ratify SALT. Let them explain how the stability of troubled regions will be enhanced by rejection of this treaty on the Senate floor. Let them explain how our security would be enhanced and how the world would be a safer place by failure to ratify SALT and by a return to Cold War confrontation...

"If SALT II contributes to our national security and diminishes the danger of nuclear war, then it will be even more important to achieve in a climate of worsened relations than in a climate of improved relations with the Soviets."

Kennedy assailed Kissinger's assertion that SALT II might leave America dangerously vulnerable to a Soviet first strike that could decimate U.S. land-based missiles and leave the greater part of Soviet offensive power intact, forcing a president to choose between self-destructive retaliation or capitulation.

"The theory is not credible," Kennedy said, because it assumed that "an American president -- having seen the devastation of 90 percent or more of our land-based missiles and the killing of 20 million or more Americans -- would hesitate to retaliate..."

Kennedy said SALT II would be beneficial in many ways, limiting both superpowers to equal numbers of weapons, limiting the qualitative improvement of missile systems, limiting the numbers of thermonuclear warheads on both sides, but also leaving the United States the option to build new weapons "to maintain the viability" of American strategic forces.

Referring to recent tumultuous events in the Middle East and Asia, Kennedy said the United States remains the world's strongest power, and that new forms of turmoil in farflung lands have "little to do with our own relative strength or weakness," but are produced by factors beyond American control.

Kennedy found a positive side to events in Iran, asserting that "at last United States policy has emerged from over a decade of exclusive political support for, and unconstrained military supply to, a repressive and corrupt regime."

Several in the audience said Kennedy's speech sounded "presidential," the sort of remark that follows Kennedy these days. He raised the subject himself in an opening quip on the Washington weather, saying, "Next time I give a SALT speech I think it will be in Georgia" -- a reference to Carter's speech yesterday.