Mr. Gromyko's explanations

President Reagan can be pleased by the fact that Andrei Gromyko went to such remarkable and unusual lengths to try to counter the offer which the President had made three days earlier on intermediate-range nuclear weapons. The Gromyko performance stands out as a tribute, albeit unintentional, to the skill and soundness of the American President's proposals and timing.

To get the two operations into perspective, notice that it is a rare event for any high official of the Soviet Union to deliver an hour-long speech live on Soviet television and submit for another hour to questions from reporters, also on television before the entire Soviet TV audience.

There are plenty of longer Soviet speeches, but not to the general audience, and not followed by extemporaneous answers to voiced questions.

Notice also that the Gromyko performance followed by three days the President's announcement that he was ready and willing to negotiate an ''interim'' agreement with the Soviets to limit, on a basis of equality in warheads, Soviet and American intermediate-range nuclear weapons in the European theater.

Up until the President's statement on March 30 the Soviets had been enjoying the propaganda advantage with public opinion in Western Europe and much of the rest of the world. Moscow had succeeded in appearing to be more interested in peace and in weapons control than had Washington. Moscow had mounted a sustained and skillful ''peace offensive'' from shortly after the suppression of Solidarity in Poland.

The more President Reagan and his lieutenants talked weapons and the possibility of winning nuclear wars the more allied and friendly opinion began to pull away from the US and to look with rising hope toward Moscow.

Mr. Reagan's ''zero-zero'' proposal for Europe was no help in the propaganda war. The elimination of all Soviet and US intermediate-range weapons from Europe is desirable and would restore the balance of weapons in the European theater to what it was before the Soviets began deploying their new SS-20 missiles, but the Soviets have by now planted over 200 of these weapons in Europe. It is not in the habit of the Russian bear to give up an advantage like this without getting something in return.

Thus, so long as the President stood on his ''zero-zero'' position there was not going to be any progress toward arms control and the Soviets would continue to enjoy the propaganda advantage. That advantage was bound to show up in the antinuclear demonstrations which come with spring and the Easter season and which make it difficult for the NATO governments in Europe to proceed with their plans for accepting the new US weapons.

The contrast between the alleged (no matter how fraudulent) flexibility in the Soviet position on weapons and the inflexibility of the Washington position assured more recruits for the peace demonstrations.

It was at this point that the President made his new offer on the weapons for the European theater. The purpose was to prove that Washington is ready and willing to negotiate for a downward limit on these weapons.

If the new Washington offer had been specious there would have been no need for anyone in Moscow to worry about it. A routine editorial in Pravda would have been sufficient to keep Moscow in the favorable propaganda position.

Therefore the reaction in Moscow was watched with greatest interest.

The answer was bound to be a no. At this stage of play there is no certainty that the European members of NATO will be politically able to accept the new American weapons they asked for. So long as there is a possibility that Europe will refuse to take the weapons, or take them with acute political pain, Moscow has nothing to gain and something to lose by going to the bargaining table.

The time for serious negotiation will come when and if the deployment of the new American weapons has actually begun. Let a few of the Pershing IIs be actually planted in West Germany and a few of the new cruise missiles start appearing on British airfields and the reason for Soviet delay will decline. But any diplomat can tell you that you don't start negotiating as long as you think you can gain an advantage from waiting.

So what did happen?

Mr. Gromyko was put before Soviet television on April 2, just three days after the President. And Mr. Gromyko launched into a brilliant, almost tear-jerking explanation of Moscow's unreadiness to go now to the bargaining table. We used to think of him as a cold fish. Mr. Reagan could not have played the role better than Mr. Gromyko did. Unless you knew the nuclear facts you could have watched that performance and concluded that the Soviets were the ''good guys'' being cheated by the mean Americans.

But note that it consisted exclusively of explanations for not doing something and therefore was not good enough to regain the propaganda advantage for Moscow.