EDMUND S. MUSKIE, who spent 21 years as a United States senator and eight months as secretary of state, met Washington Post editors for a farewell luncheon last week. Among other things, he addressed the problem of projecting American power in a crowded and dangerous world. Some excerpts:

The challenge of identifying our real interests is greater today, because more distant events can impact on them today than at any time in our prior history. And projecting military power as a way of dealing with instability, wherever it is, becomes very difficult and costly and not necessarily effective. That certainly, to me, is demonstrated by the Iranian experience.

We've had to consider the projection of military power in the last year or two not only in connection with the Iranian hostage experience but also in terms of the Soviet threat falling on Afghanistan. [Soviet Foreign Minister Andrei] Gromyko asked me, "Why are you so upset about Afghanistan?" I said, "It's the geography of Afghanistan that disturbs us. Whatever your present intentions are, if you move into Afghanistan and stay there you will become a more serious potential threat to our vital interests in the area than you were before you moved in." And this is true of Iran now. The projection of military power in the event that potential threat emerges is a question with which we are constantly confronted.

Now since 1974, when oil was first used as a weapon against us, the Rapid Deployment Force was created for the purpose of projecting military power there. But if there were an all-out Soviet offensive or attack there, that Rapid Deployment [Force] has limited utility, except maybe as a tripwire. And, of course, there's a nuclear deterrent behind it if we should decide that it was that serious in terms of our real national interest.

The consequences of a cutoff of the Persian Gulf oil, for us in the West, are too catastrophic to ignore. For me, with all the Chads and the El Salvadors, the Nicaraguas and the rest, this is a very top priorty for us.

There's constant effort to read Soviet intentions. I don't think the conclusions ought ever to be static, because they can be affected by internal developments in the Soviet Union as well as external events. That's a dynamic set of elements and pressures that one ought never to lose sight of. They're not 10 feet tall. They do have internal problems, economic problems. The don't have unlimited ability to challenge us or the rest of the world, and sometimes when we act as though we thought they did, our reactions to their behavior tend to be excessive or unrealistic. It's a very dangerous game, a very delicate game.

I can't think of a question I found more troublesome in these eight months than the occasions -- and there were many -- on which we considered what are Soviet intentions next. We constantly monitor their troop dispositions, troop movements, military exercises, and when they emerge in a new area in different dimensions and large dimensions, we have to be concerned about what they might lead to, and what we need to be in a position to do in response. And it's a worrisome business.

Their preoccupation with Afghanistan in a sense has to be moderated and now their growing preoccupation with Poland may moderate their intentions with respect to the Gulf area. They can't do both, even though both are on their borders and they're in a better position to deal with their security interests in those areas than we are to deal with their threats in those areas.

In the Pacific they are using bases in Southeast Asia that we left behind, they're building up their presence there. I think that's their interest in Vietnam, Cambodia. This gives them a position there.

How do we prepare ourselves to defend against Soviet aggression in any or all of these areas? You've got to have adequate defenses, but to what purpose? In every conceivable corner of the globe? The Horn of Africa is a worrisome thing. I suspect that with the naval forces we now have in that area that that's not likely to erupt into a major concern, but it's a place where we ought to be trying to strengthen our influence and stabilize the region to the extent that we can.