WHEN THE PRICE of oil soared in the 1970s, one great question was the use to which the oil-exporting countries would put their new wealth. Iraq and Iran have used it to pursue, for 41/2 years, an immensely bloody war. For some time it has been deadlocked along a line very close to the prewar boundary. Periodically one side or the other attempts to break the deadlock, and the level of fighting suddenly rises. That is happening again this month.

But this attempt differs from most of its predecessors. This time, in violation of an agreement worked out last June by the United Nations, both sides are going after civilian targets. Neither has sufficient air power to make a decisive difference in the military balance. Both apparently have decided to use their planes instead to increase the sense of war-weariness and fear among the civilians in the hope of generating pressure for a negotiated settlement. A series of explosions in Baghdad suggests that Iran may be using missiles against its enemy's capital.

Neither side seems likely to win a conventional military victory. Both are better equipped for defense than for offensive operations. That's why the casualties have been so high. Both sides, but particularly the Iranians with their much larger numbers, have relied heavily on tactics reminiscent of World War I, with massed infantry attacks into fire from entrenched machine guns.

The United States and the Soviet Union came some time ago to a tacit agreement that Iraq cannot be allowed to lose. Each of the superpowers has its own obvious reasons for wishing to avoid the surge of aggressive Moslem fundamentalism that would surely follow an Iranian triumph. Iran has been trying to buy weapons from every possible source from South America to North Korea, but the superpowers have been at work to hold down the flow. They have succeeded -- so far -- in preventing Iran from breaking the deadlock, but not in ending the fighting. As long as it continues, a breakthrough by one side or the other remains possible. That was what the Iranian offensive this week was attempting -- with very high losses but, apparently, little success.

The sticking point remains the Ayatollah Khomeini's insistence that any settlement must require the overthrow of Iraq's president, Saddam Hussein. There recently have been signals suggesting that at least some Iranians are ready to retreat from that condition although, like all signals from Iran, they are anything but clear. For the rest of the world a stalemate remains the best military outcome possible, since that alone seems likely to lead to serious peace negotiations.