THIS IS NOT the best time to debate who lost Iran. To begin with, that's the wrong question; the right one is whether different U.S. policies might have led to less damaging results. Moreover, a fair appraisal demands some historical perspective, and disputes over past policy preferably should await the release of the hostages.

But the debate has already begun, especially with former Ambassador William Sullivan's recent version of what went wrong. While Sullivan's account is essentially accurate so far as it goes, it is nevertheless an incomplete story that he tells. So for the sake of a better, if tentative, understanding, it might be worth considering another participant's account.

Sullivan does ask an important question: whether the United States should have acted differently between mid-November 1978 and mid-January 1979, the last two months before the shah's fall. But his account suggests another question that is at least as important: whether we should have acted otherwise at an earlier time, between November 1977 and November 1978. Sullivan was also ambassador then, a period of intense opposition to the shah.

In the last two months of the shah's rule, his probable fall should have been all but unmistakable. In mid-November 1978, for example, it became apparent that a million or more Iranians (about half the adult male population of Tehran) would march against him on Dec. 11, the Muslim holy day of Ashura.

But concerted political activity against the shah was clearly visible to Western observers a year before that, beginning in November 1977. What were the signs then and how good were Americans, both private and official, at reading them?

Before, during and after the shah's November 1977 visit to Washington, thousands of students and Western-educated professionals joined in Tehran to protest his rule. In early January of 1978, mass riots erupted in Qom to protest a government press campaign against the Ayatollah Khomeini and the death of his son under mysterious circumstances.

A month later there was a full-scale insurrection in Tabriz, in which thousands of demonstrators burned banks, modern stores, movie theaters and other visible signs of "foreign influence." From then on, mass marches, protests and demonstrations, growing ever larger and drawing the participation of Iranians from all walks of life, occurred with regular and increasing frequency until the shah's departure.

In some quarters, these signs were a cause for grave concern. On March 10, 1978, the State Department's alarmed Bureau of Intelligence and Research convened a panel of both inside and outside experts to discuss the shah's future.

The experts warned that the opposition was broad-based and that anti-shah sentiment ran deeply through the entire society. In a paper prepared for the meeting, one U.S. scholar wrote, with remarkable prescience:

". . . time is not on the side of the shah . . . those chasing him are more numerous, more dedicated, and more prepared . . . the government can now only respond with more and more coercisive force . . . the large groups of individuals already alienated by the regime will in turn become more damanding and more desperate . . . And they will be joined by others . . .

"Unless something is done to break this wildly spinning vicious circle, the future of current actors in the Iranian political drama can only be a grim one. And the American future in Iran can now in no way be considered bright."

Why, then, didn't United States policy recognize the gravity of the situation?

One major obstacle was the considerable disparity between the picture drawn by these experts and the impressions the U.S. embassy conveyed from Iran. The embassy consistently underestimated the strength and significance of the opposition to the shah. It was not until those last two months that it suggested the regime might fall.

The fact that protests were occurring, often involving large numbers of Iranians, was, of course, reported. But the embassy usually characterized the participants as a minority, representing for the most part religious extremists and radical students. It did not convey the impression that profound anti-shah sentiments were shared by a large majority of Iranians.

At the same time, the embassy seriously overestimated the degree to which the shah still retained some credibility with the Iranian masses. As a result, its reporting exaggerated the shah's ability to manage the crisis by making partial concessions designed to satisfy some opposition demands.

For example, in June 1978, the shah made a speech to the faculty of Tehran University in which he repeated earlier promises of "liberalization," including the constitutional separation of powers and greater public participation in political decisions. The embassy reported the announcement as a positive step that would help calm the opposition by showing that the shah was moving to change conditions in Iran. In fact, the promises failed to produce, on either the opposition forces or the general public, the calming effect that was predicted.

As early as late 1977, a few members of the U.S. mission in Iran began to view the opposition as a serious threat to the shah. Washington was usually not informed of those differing views. On one occasion when a pessimistic assessment was forwarded, it was in a format designed to attract a minimum of attention, and the embassy added that it did not share the reported views.

It is worth noting that the U.S. official in Iran who most accurately judged the strength of the opposition during 1978 spoke fluent Persian, while most other U.S. diplomats did not. Moreover, his daily routine brought him into contact with many ordinary Iranians, whereas others in the embassy tended to restrict their contacts to high government officials and other members of the Iranian elite.

Does any of this matter? Could a different U.S. policy between November 1977 and November 1978 have led to a better outcome? If we mean keeping the shah in power, the answer is probably not.

Had the shah's regime been different, the revolution might have taken a different path or been avoided altogether. But by the time Carter became president and Sullivan was named ambassador, there was probably little, if anything, that could be done to shape or delay forces that had been set in motion many years before. The grievances against the regime -- rampant inflation and widespread unemployment, excessive and wasteful military spending, massive corruption, and indiscriminate repression -- were too longstanding and too deeply felt.

Certainly by early 1978 the revolution was already well underway, and the fall of the shah was more or less unavoidable. Only massive military intervention, on the scale of the Soviet invasion of Afghanistan, might have saved him.

Still, there are actions that might have left the U.S. better positioned to deal with the new revolutionary government.

First, we could have established regular but discreet lines of communication with opposition leaders. Through much of 1978, figures from both religious and secular elements requested such contacts. But except for a few random meetings with secular leaders, we avoided them, a rejection which probably increased their hostility toward the United States. Moreover, once the revolution succeeded, the United States had little reliable information on such key players as Khomeini, Bani-sadr, Beheshti, Khalkhali, and others.

Second, we could have avoided the public acts that underlined the intimacy of our relationship with the shah. For example, throughout 1978 the United States issued regular public statements of support for the shah as he faced growing popular opposition. The statements, widely publicized in Iran, reinforced popular anti-U.S. feelings. Moreover, the impression was created that the United States was seeking, as it had 26 years earlier in 1952, to manipulate Iranian internal affairs to prevent the success of opposition forces.

At the same time, we pursued a weapons sales policy (strongly supported by Sullivan) that had two unfortunate consequences. The sale of massive amounts of sophisticated weaponry fed the Iranian belief that the country's oil wealth was being wasted to benefit U.S. defense companies. Moreover, the focus on high-technology weapons so absorbed the energies of the Iranian military at all levels that organization and infrastructure were never adequately developed. Had Iran concentrated on these basic building blocks, the military might not have disintegrated so quickly during the final two months.

No conceivable change in U.S. policy would have induced the revolutionary government to be pro-American. After nearly two centuries of domination by powerful outsiders (the British and the Russians before us), Iranians intensely hated foreign powers and foreign influence. A study of Iran's past suggests that current anti-American feeling is as much a product of this history as of three decades of U.S. support for the shah.

Thus, considerable hostility toward the United States was inevitable. But suppose the proposed steps had been taken some time before November 1978. b

It is important not to exaggerate what could have been salvaged. Only modest advantages might have been gained. But, as a result, the United States and Iran might have maintained correct, if cool, relations after the revolution. Given Iran's critical geopolitical position, that would be something worth having today.