Ten days after the start of the Iraq-Iran war, both the hope for early settlement and the air of immediate crisis have receded. There is growing belief among U.S. officials and private experts that it may be a long-term, low-level war, a throbbing new headache painful for the two participants and damaging to the international economy over many mohths.

Despite Iraq's reported offer of a temporary cease-fire beginning Sunday, there is no sign that the basis for settling the conflict -- or negotiations to explore such a settlement -- are in sight.

In a variety of expressions, close followers of military and diplomatic reports seem to be approaching a broad consensus that an early break is unlikely but that a continuation of the status quo will be dangerous as well as debilitating.

"This may become a war of attrition, though not at the same level of fighting we have seen in recent days . . . Both sides are going to feel pain but neither side is willing to give in," said an official monitoring the situation.

Another official foresaw "a protracted situation in which the chips are down . . . a protracted stalemate, wwith the chance always remaining for a flareup bringing greater instability and the threat of wider involvement of outside countries."

In the first rush of war news from the Persian Gulf early last week, the predominant official view was that Iraq's aims as well as its likely military operations were carefully limited, and that both Iraq and Iran had too much to lose to spread the fighting to petroleum facilities, the source of both nations' principal tangible assets.

This view was shattered when first Iran, theh Iraq, bombed oil refineries and other facilities. Moreover, Iraq moved slowly but steadily on the ground into the Iranian oil province of Khuzistan, beyond the area of active territorial claims on the border. Clearly, Iraq was after bigger game.

Official thinking next concentrated on the possibility of sharp escalation which could bring a catastrophe or crisis of worldwide dimensions. The most vivid scenarios were desperation measures by Iran: mining, bombing or other action to shut off the international flow of oil at the world's foremost petroleum chokepoint, the Strait of Hormuz, or air attacks against Persian Gulf oil sheikdoms alleged to be helping or favoring Iraq, such as Kuwait, the United Arab Emirates and even Saudi Arabia.

While these possibilities remain -- especially if Iran should come to feel hard pressed and without other cards to play -- the sense of imminent danger felt here late last week has receded.

In case of a threat to the strategic oil lanes, the expectation in official circles was that very strong diplomatic pressures from Gulf states as well as Western Europe and even nonaligned nations would be applied to Tehran. Only after this had been tried in vain would the much-discussed international flotilla be dispatched to take military action to protect the oil flow.

Iran's public statement yesterday that it does not intend to threaten the strait may reflect some of those diplomatic pressures, applied on a preemptive basis, as well as reflecting the talk of collective military action. The statement has been taken as a good sign, though the possibility of an eventual Iranian move against the strait -- estimated by some officials earlier this week at 30 to 35 percent -- has not been written off.

The threat of an Iranian strike against Saudi Arabia or other non-combatant Gulf states was never considered as great in the eyes of Washington. The Saudis, however, displayed grave concern.

The Saudi request for help in bolstering Eastern Province air defenses, conveyed in Riyadh last Saturday through Ambassador John West and Gen. David C. Jones, chairman of the Joint Chiefs of Staff, led to urgent and unannounced meetings at the White House Sunday on a proposal to dispatch Air Force airborne warning and control planes. Other requests -- and other positive U.S. responses -- for building Saudi air defenses may be forthcoming.

A diminished prospect of immediate escalation brought few sighs of relief in official quarters, however. While the danger seemed reduced of a conflict going on quickly to ignite a general conflagration, the danger seemed enhanced of a conflict going on, and on, and on.

Reports from the war zone indicate the Iraq is nearing -- and by some accounts has already achieved -- a position in Khuziatan from which it can interrupt transportation, including rail and pipeline oil traffic, between Tehran and Iran's major oilfields along the Persian Gulf. Even if Iraqi forces do not advance much deeper, such a stranglehold is likely to be intolerable to Iran economically as well as politically.

Iran, in this situation, may be unable to expel the Iraqi forces militarily and unwilling to negotiate a deal, which is certain to involve concessions, to bring about their elimination through political means. There is little expectation that Iran will accept a cease-fire that leaves Iraqi forces well inside its long-established territory.

Nor are outside forces -- whether the United States, Soviet Union or the Arab lands across the Gulf -- exerting pressure on Iraq to withdraw its forces from occupied Iran. In fact, at this point the word "withdrawal" has been hardly heard from any quarter as the Iraqis continue their slow advance into Iran along a broad front.

Unless Iraq is willing to retreat from Khuzistan of its own volition, which seems unlikely at the moment, the prospect is for protracted struggles, both military and political. It will not be a stable situation but a highly unstable one involving air and ground attacks, sabotage, inflamed hatreds and the ever present possibility of new escalation or extension of the war.

In such a struggle, each country will continue to use military power to deny the other the use of its oil assets. This much-needed petroleum will also be denied to the world at large, causing a renewal of the psychology of scarcity which in 1979 led to a re redoubling of international oil prices, with grave economic and political repercussions for many nations.