With the failure of Iran's recent marshland offensive against Iraq, the vulnerable oil-rich Arab states of the Persian Gulf have experienced another in their periodic cycles of fear, relief and renewed belief in seemingly miraculous, if only temporary, deliverance.

The pattern has remained roughly the same since soon after Iraq invaded Iran in September 1980 and discovered it was unable to win the war it had started.

For the militarily weak, sparsely populated mainstream Sunni Moslem-dominated states of the Gulf Cooperation Council -- Saudi Arabia, Kuwait, Bahrain, Qatar and the United Arab Emirates -- theirs is the politics of survival.

Their governments are backing and providing economic aid for Iraq not because they necessarily want to support Iraqi President Saddam Hussein, but because they have convinced themselves that a victory by Iran's militant Shiite Moslems would sweep them away.

At best, the gulf council states believe they are in a period of remission, their officials say. They feel that the threat of Iranian victory -- and thus of their undoing -- will come again. For them, the marshland offensive cannot be construed as even a turning point in the war.

At worst, they are caught in what is sometimes in diplomatic language called "creeping Lebanon-ization." That is the inexorable process of gradual accommodation to rising levels of violence which, as in the case of Lebanon, imperceptibly, but definitively, reaches the point of no return.

Privately, officials in the gulf have grave doubts about the wisdom or efficacy of Iraq's current efforts to force Tehran to end the war by massive atacks against Iranian cities and civilians. But their advice is not sought in Baghdad and some diplomats question whether it is even proferred to the Iraqi president, who seldom has taken their interests into account.

Thus, despite their brave public talk of favoring a diplomatic settlement of the war, gulf leaders privately fear that Iran will not stop fighting as long at its spiritual leader, Ayatollah Ruhollah Khomeini, is alive.

They recall that Iraq's air attacks on Iran-bound shipping in the now year-old "tanker war" failed to bring Tehran to heel. But it did frighten the nations of the gulf council and cause losses to its shipping when Tehran, replying in kind, attacked tankers and other vessels using ports of council states.

Now as then, the council countries keep their fingers crossed that Iran will not lash out against them in retaliation for Iraq's war on civilian targets, which Tehran wants stopped.

No council member hopes more than Kuwait that Iran has higher priorities for its depleted inventory of combat aircraft that logically would be Tehran's retaliatory weapon. Kuwait, located at the head of the gulf, is within eight minutes' flying time of the Iranian air base at Bushire.

With its population dependent on vulnerable desalinization plants and its own Air Force untested in combat in the event of an Iranian attack on them or its oil facilities, Kuwait is the perfect "soft target."

Last May, Kuwait took heart when a Saudi F15 shot down an intruding Iranian F4. Saudi Arabia also began sharing information from American-supplied AWACS electronics intelligence aircraft flying over the gulf.

In recent months Kuwait has muffled its once strident criticism of Washington's Middle East policy following the Reagan administration's refusal last spring to sell it Stinger shoulder-fired ground-to-air missiles for use against low-flying aircraft.

Only this week U.S. Gen. Robert Kingston, commander of the Central Command forces, paid his first visit to Kuwait.

But in the case of Iranian battlefield victory, diplomats and analysts doubt that Kuwait could be protected, especially if Iraqi refugeees started arriving in large numbers.

Yet, even here there is little talk of the war except in the highest government circles. A western diplomat who recently spent three days in the emirates to the south reported that officials there had not even mentioned the war in passing.

Here, there was no panic or rush to the airport when Iran appeared to be heading toward a decisive breakthrough in the marshes earlier this month.

But the keen-eared here can sometimes hear the nighttime Iranian shelling of the southern Iraqi port of Basra. And Saudi Arabia needs no reminder of the potential for renewed unrest among the Shiite minority in its oil-rich eastern province. Nor does Bahrain about its own large Shiite community.

It is not just the specter of an Iranian victory that worries the gulf Arabs.

For if Saddam Hussein were to emerge victorious, Iraq would command the largest army in the Arab world and exercise enormous influence throughout the gulf and beyond.

Even so, that that prospect is a happier one than the present state of nerves. Iran Threatens New Move; Iraq Bombs Tehran Again Deutsche Presse-Agentur

TEHRAN, March 29 -- Iran threatend a massive ground offensive against Iraq today as a top-level Iraqi delegation sought weapons in Moscow to counter Soviet-made missiles allegedly acquired by Iran.

"Iran has completed preparations to launch its expanded offensive against Iraq," parliamentary speaker Ali Akbar Hashemi Rafsanjani told Moslem worshipers during today's prayer sermons in Tehran.

He assured Iran's noncombatant neighbors that Iran had no hostile intentions toward them.

But he reiterated that Iran "will never accept a cease-fire to fighting on the battlefield," and he advised neutral Persian Gulf Arab states, which support Iraq, to "repent" by stopping their aid.

Rafsanjani's statements came against a backdrop of warnings to Kuwait by the English-language Tehran Times newspaper, which said the Kuwaitis virtually had placed themselves in "a state of war" with Iran by aiding Iraq.

Iraq reported that its warplanes struck at Tehran for the fifth day in a row. State-run television said the attacking Iraqi warplanes "returned safe and victorious, United Press International reported from Baghdad.

[Tehran Radio said an Iraqi warplane made an air raid over the city at 10:10 p.m. and fired a single rocket into a residential area, injuring three people.]