The United States has told the Soviet Union that it is prepared to support a "decent and constructive" resolution of the Afghanistan crisis that would protect the Soviets' "legitimate security interest" in that country, administration officials disclosed today.

The American effort to interest the Soviets in such a face-saving arrangement for a troop withdrawal has been made through a number of channels and was raised in Secretary of State Edmund S. Muskie's discussions in Vienna last month with Soviet Foreign Minister Andrei Gromyko.

[In Moscow, a senior Tass commentator called the U.S. proposal "deliberately vague, absolutely unclear," and accused President Carter of deception in his discussions of Afghanistan. Details on Page A21].

Thus far, one official said, there have been no indications of changes in the Soviet policy that led to the invasion of Afghanistan. But he said the American offer still stands and suggested that it may become more attractive to the Kremlin because the Afghan occupation has proved to be "more costly and more difficult" than anticipated.

A senior American official made the disclosure to reporters aboard Air Force One this morning as Carter was flying here from Belgrade on the third leg of his week-long trip to four European countries.

The official was elaborating on Carter's remarks last night as he offered a toast at a state dinner hosted by Yugoslav officials.

Carter said at the dinner that with the withdrawal of Soviet troops, the United States is prepared to "join in assurances and arrangements" guaranteeing Afghan neutrality and is also willing to explore a "transitional arrangement" leading to that result.

This suggestion by Carter, which he first made in February in a letter to the late Yugoslav President Tito and chose to resurface last night, along with elaboration provided today by American officials, put the United States in the position of publicly offering the Soviets a possible way out of the Afghan conflict.

As such, it was clearly designed to increase pressure on Moscow to begin negotiations for a troop withdrawal or drop its claim that it invaded Afghanistan only to protect its vital interests.

"The Soviets say, "We're in Afghanistan to protect a limited legitimate security interest,'" the American official said. "We say to them, 'If that's the case we'll make arrangements which permit you to leave, and if you insist on staying then obviously your interest is not a limited security one.'"

The precise nature of a "transitional arrangement" during a Soviet troop withdrawal was not spelled out, nor was it clear whether this has been discussed in any detail with the Soviets by Muskie as part of the American effort to achieve a total troop withdrawal.

But there have been public suggestions, which were reiterated today by American officials, for establishment of a peace-keeping force from Islamic nations to ensure that there is not "mas slaughter" of pro-Soviet Afghans or "massive confusion" as Soviet troops are pulled out.

The precise American role in such arrangements was also not spelled out, but officials spoke in terms of U.S. guarantees to Moscow that Afghanistan wouild not pose a threat to the Soviet Union once the troops are removed.

"We recognize that the Soviet Union has a legitimate security interest in Afghanistan not being transformed into an anti-Soviet outpost of some sort," the senior official said.

Asserting that there is a growing consensus that Afghanistan must become a truly nonaligned and independent nation as part of any resolution of the crisis, the official added:

"We are prepared, whenever the moment is right, to enter into arrangements designed to make sure that this is stable, that this is not a threat to anybody, particularly to the Soviets, who have to be reassured that if they leave, Afghanistan doesn't become, then, an outpost either for Western or American or any other anti-Soviet political-military orientation."

As outlined by this official, the American proposal calls for a guarantee of Afghan neutrality and an implicit U.S. recognition of the Soviets' interest in the neighboring country in return for fulfillment of Carter's demand for a complete troop withdrawal.

According to U.S. sources, the idea was raised in general terms by Muskie during his mid-May meeting in Vienna with gromyko. A more detailed version of the suggestion, including the idea of "transitional arrangement" during the withdrawal process, was later relayed by Muskie to Gromyko through third-party channels, the sources said.

The public surfacing of the American effort to win Soviet agreement to such a troop withdrawal arrangement came near the end of Carter's European trip, during which he has repeatedly demanded a total troop withdrawal and often used harsh anti-Soviet language. The American officials said a complete withdrawal remains Carter's "cardinal principle" but that the United States recognizes that steps must be taken to "make it possible."

"We have, therefore, publicly stated a position which indicates that a fair and peaceful solution could be found," he said. "That's the purpose of the president's statement, but we're not in a negotiating situation with them because at this stage, they themselves have to rethink what went on.We are much more in the stage of publicly stating how an eventual decent outcome could be contrived, one that the international community as a whole supports."

The official, however, said the United States has had no indications of Soviet willingess to consider the American proposal.

"It could take them a long time," he said. It's not easy to change basic decisions."