SHORTLY AFTER the 1973 Arab oil embargo, Congress established a national oil reserve, equivalent to 90 days of oil imports. The law establishing a Strategic Petroleum Reserve, written with broad bipartisan support, has been on the books ever since. But though almost everyone agrees that such a national reserve is a desirable thing to keep the country from being as vulnerable to pressure as it was in 1973, the reserve is still getting nowhere.

Today it holds about 90 million barrels -- approximately a 16-day supply at the current, much reduced rate of imports. The construction program for building additional holding capacity is about five years behind schedule -- quite a trick for a five-year-old program.

The government suspended purchases for the reserve when oil supplies tightened in the wake of the Iranian governmental upheaval. Last spring, an administration plan to begin buying again was opposed by Saudi Arabia, and the government -- dependent on an accelerated rate of Saudi oil production -- acquiesced. Congress finally lost patience last summer and required the administration to begin filling the reserve at an annual rate of at least 100,000 barrels a day. Working at this rate -- and counting the oil already in storage -- it would take 25 years to reach the goal of one billion barrels.

Why has it proved so hard to carry out a project that would both protect the country from political coercion and help it avoid economic havoc in the event of another oil interruption? One reason is that the reserve costs a lot of money and has been an almost irresistible target for budget-cutters. Another is that from the point of view of other oil-importing nations, there never is a good time for the United States to begin buying for its reserve, or to raise the rate of buying. So whenever the market begins to tighten, the first place U.S. friends and allies look for slack is the reserve, and this country is asked to stop buying to help hold down world oil prices.

The only way to break this cycle is finally to make the reserve a genuine national priority, one that transcends each year's budget-balancing act. Among other steps, this would mean substantially raising the rate at which the reserve is filled, so that the goal can be reached in a reasonable period of time. The Senate recently took a step in this direction by mandating a rate of 300,000 barrels a day, though in deference to the incoming administration it left a large loophole in the requirement. Finally, this increased rate of buying for the reserve should be met without increasing total oil imports, so that the United States does not put additional pressure on world oil prices. That will require further steps -- especially the decontrol of gasoline -- to bring down unnecessary domestic consumption. That may not seem pleasant, but it spells the difference between a greater measure of national security and continued American vulnerability to oil production in one of the world's most troubled regions.