Your move, Mr. Reagan

We are approaching a dangerous line. There is an old Russian saying: ''Even an unloaded rifle can fire once in 10 years. And once in a hundred years, even a rake can produce a shot.'' We have to keep our senses and be extremely careful.m

So said Marshal Nikolai Ogarkov in an unusual interview with a correspondent of the New York Times. It was not surprising that the chief of the Soviet General Staff used the interview to sound another warning about NATO's plans to begin deploying new medium-range missiles in December. If such missiles were ever used against the USSR, he said, ''adequate retaliatory steps'' would be taken against the United States. In Soviet eyes, in other words, the Euromissiles would be considered strategic not theater weapons.

Marshal Ogarkov and others are intensifying pressure in the context of nth-hour bargaining in Geneva. But behind all the thrust and parrying it seems evident that the Russians want to strike a deal if only the United States shows some flexibility. Marshal Ogarkov is no stranger to war and, like his compatriots, he knows only too well the dangers of unleashing another one. Certainly the Russians, no less than the Americans, do not want to see the world go over the brink.

At the same time Soviet leaders, like their US counterparts, have to worry about keeping up the nation's fighting spirit and pre-paredness. Each side therefore tends to exaggerate the strength of the other - though the Russians probably do so more because of their historical experience and feeling of inferiority. When asked once by Sen. Alan Cranston why the Soviet military tells its troops that the USSR can win a limited nuclear war, Marshal Ogarkov responded that this reflects no less a domestic political consideration than when President Reagan speaks to his far-right constituents. In effect, you cannot instill morale if you tell troops a war cannot be won. But, as he said again this week, it would not be possible to contain a nuclear war: ''Such a war will extend to all-out war.''

The question is whether the Reagan administration is prepared to take seriously the concerns and warning voiced by Marshal Ogarkov and other Soviet leaders - and to move forward on an arms pact. It is worth noting that the Russians, in their formal proposal, are not saying that the non-NATO British and French missiles must be brought into the negotiations but simply that they must be compensated for. The present strength of these independent forces is not what worries Moscow so much as the massive buildup now under way - a justifiable worry.

The Geneva talks recess on March 28. An American counterproposal put on the table before that date would reassure Europeans, help prevent West German demonstrations, and signal the growing US freeze movement that the President desires progress on arms control. Unfortunately, the administration seems too divided to produce a well-thought-out interim alternative to its initial ''zero option'' proposal; hard-line voices in the Defense Department are at odds with more moderate ones in the State Department. It is hard to see how the controversy can be resolved unless Secretary of State George Shultz begins to provide strong direction in this area.

Mr. Shultz admittedly is hard-pressed on many fronts. But the arms race relentlessly goes on, threatening long-term stability. No issue is more important. The world will not forgive the leaders of the Soviet Union or the United States if they waste much more time facing up to it and, to paraphrase Marshal Ogarkov, ''withdrawing the finger from the nuclear trigger.''