President Reagan's proposal to make new efforts to solve regional conflicts was intended as a message to the Soviet Union that progress on arms control depends on sharply reduced Soviet involvement around the world, especially in Afghanistan and Nicaragua, according to U.S. officials.

These officials acknowledged that the proposal made at the United Nations today was designed in part to regain the public relations initiative from the Soviets, who for the past six weeks have been campaigning effectively against Reagan's plan for a space-based strategic missile defense, often called "Star Wars."

But they said it also was a genuine attempt to link progress on arms control at the Nov. 19-20 summit in Geneva with Soviet willingness to stop fomenting regional conflicts beyond its borders.

A senior officials said that Reagan did not actually use the word "linkage," a term favored by Secretary of State Henry A. Kissinger during the Nixon and Ford administrations, in an advance letter he sent to Soviet leader Mikhail Gorbachev outlining the proposal. Nor did he use it in his speech to the U.N. General Assembly today.

But the revival of the concept of "linkage" was unmistakable in the Reagan approach, and it was reflected in the comments of administration officials after the speech. Secretary of State George P. Shultz said, "Nobody has suggested tight linkage, but the reality is there."

"If they [the Soviets] want truly a stable relationship with the United States, it has to be based on cooperation across the board, not just on arms control," national security affairs adviser Robert C. McFarlane said on NBC News.

McFarlane has been consulting with former president Richard M. Nixon on the presummit situation and some of Nixon's ideas were strongly reflected in Reagan's address. In an article Nixon wrote in the publication Foreign Affairs this month, he notes, "A summit agenda, therefore, should have as its first priority not arms control but the potential flash points for U.S.-Soviet conflicts." Nixon argued, as Reagan did today, that "arms control and political issues must go forward together."

Reagan listed five countries -- Afghanistan, Cambodia, Ethiopia, Angola and Nicaragua -- where his regional initiative would apply. The Afghanistan war was considered the principal target of his plan.

There is a growing belief in the administration that Gorbachev would like to find a face-saving way of reducing the immense military and economic costs of the war in Afghanistan started by his predecessors. The conflict has cost the Soviet Union and its Afghan ally more than 60,000 casualties during the last six years, according to the estimate of Pakistan President Mohammed Zia ul-Haq, and damaged Soviet relations in the Third World.

The belief that Gorbachev wants out of Afghanistan has been encouraged by conversations with Zia and other Asian leaders and perhaps by a report submitted to Reagan by Senate Minority Leader Robert C. Byrd (D-W.Va.) after he led a congressional delegation to Moscow last month.

Byrd said that Gorbachev had told him that the war would be over quickly in Afghanistan if Congress would "close its wallet" to the rebels. Byrd replied that this might happen, but only if the Soviets withdrew their troops.

A senior U.S. official said he expected the Soviets to formally turn down the Reagan plan but that it was possible that Gorbachev would follow up this rejection with serious direct negotiations with the Afghanistan rebels and their Pakistani supporters.

The official also suggested that the Reagan plan was not cast in concrete but could become a starting point that invites a Soviet counterproposal. In this respect, he said, it is comparable to the Soviet offer at Geneva arms control talks to reduce some categories of nuclear weapons by 50 percent. The United States has said the Soviet offer is not equitable but has welcomed it as a basis for negotiation. Reagan reiterated this view today when he said that "within their proposal there are seeds which we should nurture."

In the form presented by Reagan, the regional initiative would require much of the Soviet Union and relatively little of the United States. All of the conflicts listed by the president involve those in which Soviet-backed regimes are opposed by rebel forces of various ideologies. Omitted from the list are countries such as El Salvador where U.S.-supported regimes face guerrilla forces that get their support from the Soviets and their allies.

The administration's insistence that its proposal is a genuine one was undermined to some degree by the comments attributed to Indian Prime Minister Rajiv Gandhi by diplomatic sources.

These sources said that Gandhi discussed the proposal with Reagan when the two leaders met Wednesday afternoon. Gandhi reportedly said that the Soviets might be willing to withdraw from Afghanistan but that they would require "guarantees" such as a U.S. commitment to stop arming rebels in Afghanistan.

Gandhi received no commitment from Reagan and in a subsequent conversation with a senior U.S. official was told that the United States didn't want to discuss the subject at this time.

"The United States is not talking about guarantees," Gandhi was quoted as saying. "They don't want that."

If Reagan's proposal were accepted, it presumbably would lead to eventual withdrawal of U.S. military support both from the Afghanistan rebels and the counterrevolutionaries or contras fighting the Sandinista government of Nicaragua. But Reagan said in his speech that such steps were not currently under consideration.

"Of course, until such time as these negotiations result in definitive progress, America's support for struggling democratic resistance forces must not and shall not cease," Reagan said.

Whatever the immediate outcome of the president's proposal, administration officials insisted today that the president has shifted the U.S.-Soviet dialogue to a more "realistic" basis on which the Soviets no longer hold the propaganda high ground. And having seized the initiative, they say, he intends to follow up when he sits down with Gorbachev in Geneva.