Challenges to American interests in the oil-rich Persian Gulf are more likely to arise from political factors, such as the internal stability of Saudi Arabia and Pakistan and the course of Arab-Israel relations, than from a direct military challenge by the Soviet Union, according to a report released today by the Carnegie Endowment for International Peace.

"Nonetheless, judgments by leaders in the Persian Gulf about the relative Soviet-American military balance and who is and is not willing to use force will have an important bearing on their behavior," the report says. "In other words, the problem [for U.S. foreign policy] goes beyond deterring an actual Soviet attack . . . to the far more complicated task of neutralizing the political effects of Soviet military power in the area."

The 194-page report was produced by a panel of retired military leaders, former government national security specialists, businessmen, scientists, academics and journalists.

Although the panel's most timely points deal with the Persian Gulf, the report also says:

"There are serious problems in estimating Soviet defense costs." Spending comparisons with the United States "are of limited value" and can "be very misleading." While such U.S. intelligence estimates are acceptable for showing general trends, the limitations of these comparisons are overlooked in political debate, and a more realistic assessment must focus on other factors.

Contrary to a view frequently expressed, the NATO forces in Europe "probably would fare acceptably well in defending against a standing-start attack from the [Soviet-led] Warsaw Pact." But the allies would face "a considerably more difficult task" if an attack came after Warsaw Pact forces had even a short time to mobilize. Here, too, the problems for the West are mostly political. Would the 15 NATO nations be able to act quickly enough to mobilize themselves and would France, which is outside NATO's military command, join with the allies?

At sea, the western navies "have more and better" capabilities than Moscow and its allies have, although the West also has a far tougher job in terms of keeping ocean supply lines open. But the big question is what should be the role, size and composition of the U.S. fleet?

In the Persian Gulf, the report says, there is an American consensus on the need to deter the Soviets and build up U.S. forces, but this does not constitute a strategy. To produce a strategy, one question that needs to be addressed is whether to continue emphrasizing the Soviet threat or to give more priority to coping with the political and economic instabilites in the region.

In another finding that contradicts some other commonly held assessments, the panel said there are so many uncertainties about the outcome of a Soviet-American armed clash in the area that Moscow "could not count on a successful attack, let alone a swift or easy victory." The exception is in northern Iran, which would be hard for U.S. forces to reach and which is near major Soviet troop concentrations across the border.

On the other hand, the report says Moscow "likely would prevail" if the conflict were prolonged and the Soviets were willing to commit forces from other theaters. A key factor in the outcome for the West, however, would be which countries would join the battle and on whose side -- a question not easy to answer, the panel says.