The good news after the Easter weekend is that the door is still open to nuclear arms negotiations. Soviet Foreign Minister Andrei Gromyko struck a moderate posture in his response to President Reagan's proposal for an interim agreement limiting Soviet and US medium-range missiles. True, he termed the offer ''unacceptable'' and elements of it ''absurd.'' But the tone of his comments - made in a rare televised press conference - was one of relative reasonableness. Especially after Mr. Reagan had heated up the public rhetoric by dubbing the Soviet Union the ''focus of evil.''
No doubt Mr. Gromyko is wooing European public opinion. But his restraint in the face of what might have been taken as a US rhetorical ''provocation'' suggests that the Kremlin is serious about reaching an arms control agreement and still wants to do business with an American administration despite Mr. Reagan's tough approach.
Encouragingly, too, the antiwar protests across Europe at the weekend may have helped bolster the chances for forward movement in Geneva. Demonstrations took place in West Germany, England, Scotland, Italy, Switzerland, and the Netherlands, but they were relatively limited and cannot be said to have overfulfilled the demonstrators' expectations in every instance. Russians are thus on notice that they cannot count on winning over European opinion, dividing the Western alliance, and preventing deployment of the new NATO missiles. President Reagan, on the other hand, still cannot rule out the possibility of potential social unrest and political instability if the superpowers make no progress in Geneva come May. Both sides are thus under pressure to negotiate.
Obviously both sides have legitimate interests. Mr. Gromyko touched on the fact that the US does not take account of independent British and French nuclear forces in Europe or of US aircraft in Western Europe - an understandable concern. He also observed that the US proposal does not consider Soviet security vis-a-vis China as well as US nuclear bases in Asia. The latter is not a theme the Russians wish to strike too loudly for, if they play up a Soviet military buildup in Asia, they may risk inviting Japanese remilitarization. But certainly security on their eastern flank has to be considered.
Nor can one be entirely callous to Mr. Gromyko's reminder of the threat which Moscow would feel from the emplacement of nuclear missiles in West Germany that could reach hardened Soviet targets in six minutes. From Moscow's point of view, the new Pershing IIs would constitute a new strategic US nuclear weapon right on their doorstep (while their own SS-20s cannot, of course, reach the United States).
The Soviets have only themselves to blame for the present state of affairs, however. They risked a NATO response when they began deploying the triple-warheaded SS-20s - of which there are at present 351 - and now must live with the consequences. If Mr. Gromyko puts himself in the place of Chancellor Kohl or other European leaders, he will appreciate that they cannot stand by in the face of an unprovoked Soviet nuclear buildup at a time when the US no longer has strategic nuclear superiority. Some counterbalancing move is essential, not for military reasons but because of the political implications of doing nothing.
It seems doubtful that the two sides will agree to remove all the medium-range weapons now in contention. But, as a first step, they could at least scale back their numbers and achieve that ''equality of security'' Mr. Gromyko speaks of. After the events of recent days, there remains reason for hope.