A group led by senior officials of previous administrations that plans to lobby for Senate approval of a new strategic arms limitation treaty (SALT) with the Soviet Union announced its existence yesterday.

The group, "Americans For SALT," hopes to raise $200,000 to build public and senatorial support for the still-unsigned arms agreement.

Among its co-chairmen are Clark Clifford, Washington lawyer and secretary of defense in the Johnson administration; Townsend Hoopes, under secretary of the Air Force under President Johnson; Henry Cabot Lodge, ambassador to the United Nations, Vietnam and the Vietnam peace talks in the Nixon administration; and Charles W. Yost, ambassador to the United Nations under Nixon.

Hoopes and Yost will be the most active "executive co-chairmen" of the organization.

This is the first avowedly pro-SALT lobbying group to emerge. A number of conservative organizations and another group composed largely of former government officials, "The Committee on the Present Danger," have long been active in criticizing the SALT II agreement, which the United States and the Soviet Union have been negotiating for several years.

In a statement of the new group's intentions, Hoopes and Yost said "ratification of SALT II is supremely important to the safety and interests of the American people" and "a critical step towards further, more comprehensive nuclear arms control."

Failure to ratify SALT II, Hoopes and Yost contend, "would lead inevitably to an escalation of political tensions... and to sharp increases in strategic nuclear arms expenditures by both countries. An arms race thus unrestrained... would undermine the present strategic balance and pose grave new dangers..."

Members of Americans for SALT said they had planned to announce the organization's existence at the time a new agreement with the Soviets was approved, but decided they could not wait much longer. "It was hurting our credibility," Hoopes said in an interview last week.

The group opened a small office on Capitol Hill late last year and has recruited a staff of five. Later it plans to add field organizers, who will travel around the country trying to build grassroots enthusiasm for SALT II.

The group's greatest asset, Yost said, is popular support in the country for the idea of arms control agreements with the Soviet Union. He noted that public opinion polls regularly show about 75 percent of the public favors such agreements.

Hoopes and Yost said the group will continue to solicit prominent Americans in hopes of persuading them to lend their names to Americans for SALT.

Among those who have already agreed are: Milton S. Eisenhower, former president of Johns Hopkins University; Benjamin L. Hooks, executive director of the NAACP; Donald M. Kendall, chairman of Pepsi-Co., Inc.; George C. McGhee, former undersecretary of state; Glenn T. Seaborg, former chairman of the Atomic Energy Commission; Sargent Shriver, Democratic candidate for vice president in 1972; and Jerome B. Wiesner, president of the Massachusetts Institute of Technology.