BECAUSE the war between Iran and Iraq shows no signs of coming to an end, Americans need to begin thinking about the implications for the flow of fuel. That's hardly the largest consideration in this war. Lives are being lost there, and if the fighting should spread to other Persian Gulf countries the dangers would be incalculable. But the war is beginning to threaten the uneasy balance of the gasoline supply.

There's no immediate emergency. Stocks are very high throughout the industrial world and, except for the two combatants, the exporters of oil are still exporting at normal rates. Saudi Arabia is, in fact, exporting a bit more than normal. There's no point in trying to guess when a squeeze might arrive. The important thing to grasp is th at it could come as early as next spring, or at anytime later -- depending on circumstances over which this country has utterly no control.

What can the country do to protect itself? The president can do one thing immediately, on his own authority, and that is to decontrol gasoline prices. Without price controls, there will be no gasoline lines. Perhaps you don't want to pay more for gasoline. Neither does anyone else. But would you rather spend time in line?

In his most important and courageous contribution to energy policy, President Carter decided last year to decontrol crude oil prices. Taking the controls off gasoline prices now would be in line with that basic policy. The present moment is a good one. There's plenty of gasoline around at the moment, and decontrolling would have no immediate effect. It would have no effect at any time, for that matter, unless supplies got tight. In that case, to be sure, prices would rise faster -- perhaps much faster. But would you really rather face the lines again?

If President Carter does not act now, President Reagan will need to move promptly -- no later than lunchtime on Jan. 21 -- to lift price controls. Perhaps he will want to ask Congress for standby authority to supply essential services in a truly dire shortage. But in a relatively mild squeeze, like the one in the spring of 1979, price controls and the accompanying allocation rules demonstrably make the disruption and harassment much worse. The United States was the only country in the world that experienced long gasoline lines that spring.

For the time being, there's plenty of oil. There's an assured supply to keep homes warm, and factories running, this winter. But in the longer future, if the war continues, that assurance fades. No one in Tehran, or perhaps in Baghdad either, seems to be strong enough to negotiate a peace. Sooner or later, you can expect the effects to reach your neighborhood filling station. As for gasoline prices, with or without controls you can expect them to keep going right on up.