UNITED NATIONS, SEPT. 23 -- Soviet Foreign Minister Eduard Shevardnadze called today for an immediate cease-fire in the Persian Gulf war between Iran and Iraq and the simultaneous appointment of a U.N. commission of inquiry to assess blame for the conflict.

Shevardnadze's proposals for dealing with the war fell notably short of the worldwide arms embargo against Iran which is being sponsored by the United States.

The Soviet foreign minister, in spelling out Moscow's views on Persian Gulf hostility and diplomacy in greater detail than before, did not rule out the embargo that the United States is seeking. His remarks instead seemed to add up to an alternative approach which is less confrontational against Iran.

Soviet Foreign Ministry spokesman Gennadi Gerasimov said that "in principle we have nothing against an embargo," but he added that efforts to obtain a cease-fire and set up a tribunal to study the origins and conduct of the war should be tried because Iran seems interested in this idea.

Iranian President Ali Khamenei, while insisting on Iran's right to retaliate for the U.S. attack on a mine-laying cargo ship Monday night, said "we in no way want to start an all-out war with the United States."

Khamenei, speaking at a press conference, said his government was prepared to accept the verdict of a "competent tribunal" that would judge who was to blame for the war. But he also stressed that "a principal problem remains punishment of the aggressor before a cease-fire can come into effect."

Khamenei said his government "objected to, but did not reject" a U.N. resolution urging an immediate cease-fire and a return by all troops to international borders. "We have not closed the door to negotiations," he said.

Khamenei dismissed the risks of an arms embargo being considered by the Security Council if Iran does not accept a cease-fire, saying Iran has captured much of its weaponry from the Iraqi Army and "will always be able to find arms sellers" to fulfill the rest of its needs.

An immediate cease-fire and "exploration" of a U.N. commission of inquiry were both elements of the July 20 resolution adopted by the Security Council in an effort to stop the war. The idea of an inquiry was an olive branch to Iran.

U.N. Secretary General Javier Perez de Cuellar in Tehran in mid-September proposed that the cease-fire take effect simultaneously with the beginning of the commision of inquiry, which is the same as the idea proposed by Shevardnadze today. Iran, however, has not accepted the arrangement.

The sudden flare-up of military action in the gulf and the unyielding position here this week of Khamenei have increased the pressure for an arms embargo and diminished the hope among diplomats that a tacit or open cease-fire involving Iran can be worked out.

European diplomats said tonight that Khamenei and his aides had made only minor concessions in their private talks with U.N. officials, with no shift in the Iranian position on the central issue of a cease-fire.

Shevardnadze, in talks in Washington last week, and other Soviet officials in earlier talks, had deferred taking a position on enforcement measures against Iran, saying that U.N. diplomacy must be given time to work. Today's declaration by Shevardnadze went further but still fell short of a clear posture on the U.S.-sponsored embargo.

The Soviet Union, along with the United States, Britain, China and France, are the five permanent members of the U.N. Security Council and they have the right of veto over any enforcement measures such as an arms embargo. Late today the U.N. ambassadors of these five nations met with Perez de Cuellar to begin formal discussion of future moves. The five foreign ministers, including Shevardnadze and Secretary of State George P. Shultz, are to meet Perez de Cuellar here Friday.

After hearing Shevardnadze's proposals, Shultz arranged to meet him Thursday afternoon to discuss the gulf.

Shevardnadze's speech to the U.N. General Assembly did not criticize the United States for attacking and seizing the Iranian ship in the Persian Gulf Monday, nor did he condemn Iran for laying mines or Iraq and Iran for other attacks on gulf shipping.

Instead, Shevardnadze repeated in restrained tones Moscow's general criticisms of the U.S. naval buildup in the gulf, saying that "the greater the military presence, the higher the probability of yet another conflict and of involvement in it of a state not belonging to the region," such as the United States.

In a related development, however, the chief of staff of the Soviet armed forces, Marshal Sergei Akhromeyev, was cautiously critical of Iran's mining activities in the Persian Gulf. During a televised discussion on ABC-TV between U.S. lawmakers and Soviet officials last night, the marshal was asked about the U.S. raid against an Iranian vessel caught laying mines. "It is difficult to say if Iran was caught red-handed," he said. "We were not there. But if it were the case that the Iranians were laying mines, there is no justification. It would be a violation of international law."

Shevardnadze said today that Moscow would support formation of an international force under the U.N. flag to ensure the safety of navigation in the gulf. The United States has opposed previous Soviet suggestions to internationalize the defense of the gulf on grounds that these are efforts by the Soviets to obtain a greater role in an area of vital interest to the West.

The Soviet minister gave special emphasis to the point that unity of the Security Council's 15 members is "extremely important," and his spokesman said this applied especially to the five big powers who are its permanent members. This seemed to be an appeal to Washington not to get too far ahead of Moscow in pushing for the embargo.

The U.S. demand for an arms embargo against Iran was made explicit yesterday by Shultz in responding to the U.N. address of Khamenei.

British Foreign Minister Geoffrey Howe, who has also called for the arms embargo, said today that it is "essential now to start work" toward that end. Howe announced the shutting of the Iranian military procurement office in London in retaliation for Monday's Iranian attack on a British ship.

French Foreign Minister Jean-Bernard Raimond hinted in his U.N. address that France, which recently broke diplomatic relations with Iran, will support the arms embargo.

Chinese Foreign Minister Wu Xueqian, in his U.N. policy address today, called on Iran and Iraq to stop fighting immediately and implement the July 20 Security Council resolution "in real earnest."

A major arms supplier to Iran in recent months, China has not made known its attitude about the arms embargo.

Shevardnadze's U.N. address was more measured in tone toward the United States than many Soviet utterances in the forum of the world body, and it made much of the U.S.-Soviet "agreement in principle" to conclude a treaty eliminating medium-range and shorter-range nuclear missiles.

At the same time, Shevardnadze seemed irritated by President Reagan's presentation to the U.N. Monday and went out of his way to respond to Reagan at several points, including a quotation from Soviet scientist and dissident Andrei Sakharov opposing Reagan's advocacy of his Strategic Defense Initiative.

Responding to Reagan's advocacy of "entrepreneurial energy" and "free markets," Shevardnadze pointedly declared that "this rostrum is not a pulpit for preaching 'free enterprise'" or a schoolroom from which to "lecture the international community." He also disputed Reagan's view of regional conflict, saying, "It is heartless to recruit and arm mercernaries, to proclaim them freedom fighters and to pay millions of dollars for the murders committed by them."

State Department spokesman Charles Redman said the United States was encouraged by some of Shevardnadze's remarks but disappointed by others. "The sarcasm about the president's speech seems particularly misplaced," he said.Special correspondent Michael J. Berlin contributed to this report.