THE immediate reaction most of us had to last weekend's downing of an Iranian jetliner by a U.S. Navy warship was one of deja vu. The comparisons with the Soviet Union's shooting of a Korean Air Lines passenger plane with 269 people aboard over the Sea of Japan in 1983 proved too tempting to pass up: both passenger planes were off-course and reportedly did not (or could not) respond to military warnings, both superpowers ended up shooting down civilian planes and receiving world-wide condemnation for their action.

The point of the comparison is to suggest that U.S. policy in the Gulf is such that it will lead to immoral acts, and thus that America should pull its forces out of the region.

But perhaps the more relevant comparison--at least to explain why Captain Will C. Rogers III shot at the mistakenly-identified aircraft--is the U.S.S. Stark tragedy of just over a year ago. In that incident, Capt. Glenn R. Brindel failed to respond to Iraqi planes attacking his ship, and 37 members of his crew died as a result. After an ensuing investigation, Brindel was forced to retire from the navy.

The lesson properly taken from that incident was not that the U.S. was too vulnerable to remain, but rather that new rules of engagement were needed to allow ship captains more leeway to defend their crews against hostile forces.

The lingering memories of the Stark tragedy, combined with the fact that Captain Rogers had just completed a shooting match with Iranian gunboats and the recent revelations that the airliner may have been using a military radio code all played a part in his fateful decision.

Obviously, both the Stark and Vincennes tragedies highlight the dangers and high risks that inevitably accompany U.S. policy in the region.

BESIDES providing compensation for relatives of the victims of this tragedy as an expression of our grief and sympathy, the most important thing for the United States to do now is to come up with a credible strategy so that Navy captains are not forced to either jeopardize their crew or feel obliged to shoot at planes before they have time to identify them. But that's a point of relative detail.

Those critics who see in last week's tragedy a symbol of the bankruptcy of America's overall Gulf policy, however, are misguided. They are not unjustified in saying that the Stark and Vincennes tragedies show the Navy's poor preparation for the mission and the policy's lack of definition and reactive character. But they fail to acknowledge its fundamental soundness and general effectiveness.

The U.S. should not bow to the calls of Iranian radicals that it depart from the Gulf with its tail between its legs and leave the two parties to slug it out by themselves just because of this incident. That would only guarantee an Iranian victory while a negotiated end to the Iran-Iraq war, with victory for neither side, should be the aim of any U.S. policy in the Gulf. If nothing else, the current U.S. presence has restrained and isolated Iran, keeping that fundamentalist regime from achieving the status of a regional superpower.

After initial worries, this policy has won the support of the gulf states and of many Western allies who have dispatched their own warships to further our efforts. So far, none of these countries have denounced the U.S. for the tragedy and for our overall role in the Gulf.

Granted, the joint U.S.-international presence in the Gulf will not, by itself, quell Iranian revolutionary ambitions or safeguard the region's oil reserves. Other steps are desirable as well, such as an international arms embargo and a boycott of Iranian oil. The only problem is that, so far, such diplomatic efforts have stalled, as China and the Soviet Union have refused to join an arms embargo.

BUT the alternative to the current policy, a unilateral American pullout from the Gulf, would merely take the pressure off Iran at a point when it is feeling the full impact of a war it has glorified, enhance the stature of those radicals in Iran who call for violence and not negotiation, and weaken U.S. credibility once again in the Middle East. No wonder Iranian officials are seizing the initiative after this incident to demand an American withdrawal.

While the Stark and Vincennes tragedies underscore the difficulties inherent in any international peacekeeping attempt, they should not be used as an argument against the existing policy.