Sanctions against Iran-tough enough?

President Carter's decision to impose new sanctions against Iran is apparently designed as much for American and world consumption as it is for any real impact on the Iranians.

Indeed while the new sanctions are tougher than Mr. Carter had originally planned, they are still not expected to have any immediate or tangible effect on the Iranian militants' continued detention of 50 Americans at the US Embassy in Tehran.

President Carter announced April 7 that the United States was breaking diplomatic relations with Iran, curbing exports to that country, and ivalidating all visas for Iranian students. Mr. Carter declared the new measures against Iran were being taken in light of the Iranian government's refusal to take custody of the hostages, which he described as a "new and significant" development.

"This lays bare the full responsibility of the Ayatollah Khomeini and the Revolutionary Council for the continued illegal and outrageous holding of the innocent hostages," he said. The Iranian government, he added, "can no longer escape full responsibility by hiding behind the terrorists at the embassy."

The President left open the possibility of further action against Iran beyond the steps announced should Iran fail to move toward release of the hostages.

He said the steps he ordered April 7 were those that were necessary now but "other action may be necessary if these steps do not produce the prompt release of the hostages."

Mr. Carter said the US had acted with exceptional patience and restraint in the 156-day-old hostage crisis and would continue to consult allies and other on allied and others on his decision and additional measures that might be required.

"I am comitted to resolving this crisis," he asserted. "I am committed to the safe return of the hostages and the preservation of national honor."

Under the President's action, the 35 Iranian diplomats remaining in the US will be required to leave by midnight April 8.

Beyond the original plan for new sanctions, largely because the original plan was being regarded as little more than a symbolic slap at Iran.

Mr. Carter's original plan did not entail a complete break in diplomatic relations. But it did envisage a cutback in Iranian diplomats stationed in the US.

The original plan also did not include a curb on exports of food and medicine to Iran. But according to United Press International, the US exported no food to Iran during the entire month of February. Exports of medical supplies to Iran during the same month amounted only to about $200,000 according to one estimate.

Other US exports to Iran have been limited to items such as industrial paints , disinfectants, refrigerators, radio transceivers, tractor parts and ball point pens.

Despite the new measures, administration officials seem resigned to the Iranian government's apparent decision not to move to resolve the hostage question until after Iran's parliamentary elections are completed some two months from now.

But as most administration officials see it, there are limits on tough Mr. Carter can get without either endangering the hostages or pushing Iran closer to the Soviet Union.Thus, Mr. Carter still appears to be ruling out direct military action against Iran.

Officials also have rejected the idea of setting a deadline for release of the hostages, something which at least one presidential candidate, Ronald Reagan , has suggested. An official said that it was irresponsible for Mr. Reagan to propose a deadline without saying what he would do once the deadline expired.

One expert involved in drafting earlier plans for economic and financial sanctions against Iran said that as President Carter made his decision to impose new sanctions against Iran he obviously had American public opinion and American politics in mind. The public was growing impatient. But the expert said that Mr. Carter also had to be concerned about world opinion and the growing impression that the US was incapable of taking any action on Iran. He asserted that US credibility was on the line.

Some other experts disagree. They think that any further economic or financial sanctions against Iran will be "counterproductive" and may not only help to undermine "moderates" in the Iranian Government but may also help to drive the Iranians into the arms of the Soviets.

"There clearly are factions in Iran which want closer relations with the Soviet Union," said Roger Fisher, a Harvard University law professor and expert on international n egotiations. "The more hostile we are toward Iran, the more we strengthen those factions."

Regardless of what the US decides to do in the realm of economic and financial sanctions, there are definite limits on the impact which this can have on Iran. US trade with Iran was already reduced to a trickle months ago. Iran has plenty of money coming in from its oil exports, and boycotts tend to fail against countries with such buying power. Rhodesia survived for more than a decade against United Nations-imposed sanctions.