President Carter yesterday announced a new list of U.S. economic reprisals against Iran, and declared that if these and allied pressures fail, "the only next step available that I can see would be some form of military action."

Carter's statements at a news conference edged the United States notably closer to a decision on blockading or mining the Iranian coast in an effort to force the release of the U.S. hostages in Tehran.

Although the White House has publicly held out the option of military action since last Nov. 20, Carter and other high officials took pains in the past to say that less dangerous measures of an economic and political nature were not yet exhausted.

Carter's statements yesterday, combined with the earlier informal announcement of a major U.S. "reassessment" of the hostage crisis by mid-May, brings the possiblity of military action into view more closely and tangibly than ever.

Although reporters did not ask what the possible military steps might be, Carter volunteered that news reports and "just common sense" indicated that "the interruption of commerce with Iran is the kind of step that would be available."

Carter made clear that he has not given up hope that continuing U.S. pressures, augmented by similar economic and political pressures from U.S. allies and other friendly nations, will bring about release of the hostages before a military decision is necsesary. Part of the reason for the open talk of possible military action, in the view of U.S. officials, is to spur the allies to stronger measures.

The desire to provide new examples of nonmilitary action to the allies, as well as the desire to provide the appearance of forcefulness and momentum in the midst of the presidential primary campaign, are believed to be factors behind the list of new economic measures Carter announced. The measures were:

Prohibition on all financial transfers to Iran except for family remittances and funds related to gathering news. Financial dealings were already very small following the freeze on Iranian assets in November and additional restirctions announced April 7.

Ban on all imports from Iran to the United States. Exports to Iran except for food and medicine were barred by Carter April 7. Analysts described remaining imports as negligible. Import of oil, the main item purchased by the United States from Iran, was barred Nov. 12.

Prohibition on travel by American citizens to Iran, except for journalists. Carter called on journalists voluntarily to minimize their presence and activities in Iran.Hostage families and others seeking to travel to Tehran will need authorization from the State Department, Carter said.

A change in the status of military equipment previously ordered from the United States by Iran. Carter had impounded it in November. Yesterday, he said it would be made available for use by U.S. military forces or for sale to other foreign countries.

A request to Congress for authority to use the $8 billion in frozen Iranian government assets to pay reparations to hostages and their families, to satisfy commercial claims against Iran and to reimburse the United States for military costs because of the hostage crisis.

An administration official said Carter may seek to charge Iran for the added cost this year and next of the U.S. buildup in the Indian Ocean. This comes to a little more than $1 billion.

In general, economic analysts said the newly announced measures were essentially symbolic because U.S. commerce and other dealings with Iran were already minimal. The most potentially important step, the request to use Iranian assets for other purposes, was described as only "discretionary authority" rather than definite action.

Beyond these economic measures, Carter said he will proceed to two additional nonbelligerent steps if the hostages are not released "soon." One of these is the formal ban on shipments of food and medicine, a measure that originally was including in the list announced yesterday. White House officials said it was withheld at the last minute on policy grounds at the recommendation of Secretary of State Cyrus R. Vance.

The other nonmilitary step reserved for the future was a request to the Inelsat, an international body of more than 100 nations, to bar Iran's use of global communications facilities. A two-thirds vote of the nations is needed for such action.

Carter denied under questioning that yesterday's Iran-related announcements and others of the recent past were timed to influence the presidential primaries, where he is pitted against Sen. Edward M. Kennedy (D-Mass.).

"I would like to you to look at the calender since the first of January and find a time [that] wasn't immediately before or immediately after a primary," he said. He added, "I have never designed the announcement of an action to try to color or modify the actions of voters in a primary."

Carter said his optimistic statement on April 1 about a transfer of the hostages, a statement delivered as voters were preparing to go to the polls in Wisconsin and Kansas, was made at "a completely appropriate time" due to developments in Iran. The effort to transfer the hostages collapsed three days later.

In answer to another question, Carter confirmed that his senior political aide, Hamilton Jordan, has been involved in the attempts to convince Iran to release the hostages. But Carter seemed to quarrel with suggestions that Jordan played a key negotiating role, and said he knew nothing about reports of his aide using disguises and wigs on secret missions.

Carter's discussion of the Iran crisis touched on its potential for broader conflict at several points.

He made explicit, as have several of his senior aides, that the United States and its allies are seeking to convince Iran that it is becoming "increasingly isolated" from the world and "increasingly vulnerable to dissention and fragmentation within, and to danger from without, particularly [from] the Soviet Union, north of Iran."

Assessing the risks to U.S. allies of a military blockade or mining that would cut off their Iranian oil imports, Carter said that Iran's oil shipments have "dropped precipitously" already because of economic sanctions and strains. Thus a cutoff would be "an inconvenience" rather than "a devastating blow" to U.S. allies, he said.

Carter gave little credence to a suggestion that the Soviet Union could thwart a U.S. blockade by sending supplies into Iran via road or rail. The quantity of goods that would be denied by a possible blockade, the president said, could not possibly be replaced via the "limited transportation routes" overland from the Soviet Union or other adjacent countries.