Aftershocks of Iran, Afghanistan, Camp David

Although President Carter has not openly said so, his next step in the hostage crisis might well be a naval blockade of Iran. Much may depend on America's Western European allies; they now are being asked to go along with Mr. Carter's trade embargo of Iran.

Iran is much more dependent on trade with Europe than with the United States. But some close observers of Iran contend that even if the Europeans do go along with the embargo, Ayatollah Khomeini will remain unyielding. He is simply not likely to be susceptible to that kind of pressure, they say. That might only leave the option of a naval blockade. Such a blockade would further reduce Iranina imports and cut off Iran's exports of oil.

In announcing sanctions against Iran April 7, President Carter declared that "other actions may become necessary if these steps do not produce prompt release of the hostages."

Proposals for military action against Iran proper have been repeatedly ruled out by administration officials because such action might place the hostages' lives in danger. Such action also would run the danger of causing a major loss of life among Iranians and generating a storm of negative reaction elsewhere in the Muslim world. A blockade of the Persian Gulf straits, on the other hand, would not necessarily entail any loss of life.

But this is much easier said than done. A blockade might prove to be a riskier matter than it would have been several months ago. For one thing, the Soviet Union has, since the invasion of Afghanistan, better positioned itself to act as a "protector" of Iran. The official Soviet news agency Tass accused President Carter April 8 of issuing "direct threats" against Iran.

A blockade runs the risk of driving the Iranians into the arms of the Soviets. As a congressional specialist on national security affairs put it: "If the Soviets got through that blockade with just a couple of loaves of bread, they'd look like heroes."

And a blockade also might be extremely damaging to Western Europe and Japan because of their dependence on Iranian oil.

Japan, which has to import 99.8 percent of its oil, was until recently obtaining about 10 percent of its annual supply from Iran.

Other experts point out, however, that his dependence has diminished in recent months, thanks to a marked decline in Iranian oil exports. At the same time, there is no shortage of oil at the moment from other sources.

John Lichtblau, executive director of the Petroleum Industry Research Foundation Inc., said recently that Iran was actually exporting only about 1.5 million barrels of oil a day. That figure is considerably lower than the figures that have been cited by Iranian officials.

L. Dean Brown, president of the Middle East Institute in Washington, says he thinks nonetheless that if the Western Europeans and Japanese lose their Iranian oil imports as a result of sanctions against Iran, the US must be prepared to make up the loss.

Iranian officials already have threatened to cut off exports to the Europeans if they agree to a trade embargo against Iran.

A loss of Iranian oil imports might cause the Europeans and Japanese to invoke an International Energy Agency agreement whereby the allies share in making up any major loss. This agreement can come into play, following consultations, should the oil supply drop 7 percent below normal consumption.

Some sources think that the Europeans will try more diplomatic pressure on Iran, aimed at securing the release of the American hostages, before they decide on such a serious step as economic sanctions. State Department officials have indicated that the decisionmaking process on the issue might take several weeks. But department spokesman Hodding Carter III warned April 8 that "the threat in Iran is aimed at everybody. If this violation of international law is not overcome, then we are all hostages."

American officials have been deliberately vague about what "other actions" the US might take beyond the sanctions announced by President Carter April 7. They apparently see some advantage in keeping Iran guessing. But one official told a reporter that if the Western Europeans and Japanes did not take adequate steps of their own against Iran, the US might be forced to act in a way that would cut off Iranian oil.

Another official, speaking in a briefing for reporters following the President's statement on Iran, insisited, however, that the use of force against Iran was not necessarily the next step.