Hanging over the deliberations of Western governments, as they ponder the wreckage of US policy in Iran, is the industrialized world's absolute dependence on Middle Eastern oil.
Loss of Iran's oil, which by now is a relative trickle in any case, would be a minor burden, and it would be shared out by the 20-member International Energy Agency (IEA).
But a complete shutoff of Persian Gulf oil, including that of Saudi Arabia, Kuwait, Iraq, and the United Arab Emirates (UAE), would deal a devastating blow to the economies of the United States, Japan, and Western Europe.
Prolonged loss of Arab oil would plunge Western nations into deep economic depression by denying them the chief source of the fuel on which their industrial societies run.
Currently the United States, which no longer gest any oil from Iran, derives about 20 percent of its total petroleum supplies from Arab wells -- a much higher proportion than in 1973, when Arab countries embargoed oil shipments to the US.
Japan and Western European nations are in far more perilous straits, with the bulk of their oil supplies coming from Middle Eastern lands.
This underscores the extreme reluctance of US allies to follow President Carter down a road of tough sanctions against Iran, which might contribute to rising tension throughout the Muslim Middle East.
A number of conservative Arab governments, including those most friendly to the West, feel threatened by hot winds of Islamic militancy blowing down from Iran.
The governments of Saudi Arabia, Kuwait, and the Persian Gulf sheikdoms are Sunni Muslim, with little sympathy per se for the Shiite brand of Islam prevalent in Iran.
But large numbers of Iranians work in Kuwait, Bahrain, and the tiny principalities of the UAE. Many thousands of antiroyalist Palestinian Arabs live and work in Saudi Arabia and Kuwait.
The Saudi royal family, in particular, was shocked by the well-organized takeover of the Grand Mosque at Mecca, Islam's holiest shrine, by Muslim radicals last year.
For all these reasons, governments of Gulf Arab states hesitate to support of the US.
Analysts warn that a combination of factors could bottle up the narrow Strait of Hormuz at the foot of the Gulf through which pass the tankers that fuel Japan and the West.
* In the event of war between Iran and the US, Iranian military forces might close the Strait of Hormuz by sowing mines and/or sinking ships in the channel.
* This also could result, if the quarrel between Iran and Iraq -- bitterly hostile neighbors -- erupts into war.
US Defense Secretary Harold Brown, speaking Sunday on "Face the Nation" (CBS-TV), discounted the feasibility of Iran closing the strait, saying: "We [ would be able to] handle that from a military point of view."
* Short of war and of a blockade of the Gulf, Arab oil powers might curtail petroleum shipments to the US or to other Western allies, if the Iranian crisis appeared to take the form of an Islamic-Western struggle.
As members of the IEA, the US and 19 other industrial powers have agreed to share available crude equitably in case of a shortage of 7 percent or more of normal oil supplies.