There are two kinds of negotiations about the control of deadly weapons. First, there are those which use arms talks as a platform for propaganda. Second, there are those in which both sides are serious about trying to find limits on an arms race.
Since the Soviet invasion of Afghanistan in 1979, there has been a great deal of the first and very little if any of the second kind of arms negotiations.
This week there are signs that at last both Moscow and Washington are beginning to think about possibly going over from making propaganda out of arms control to actual and serious thinking and talking about arms control.
The hardest single fact is that out of a blue sky the Soviets made on June 29 a formal and official proposal to Washington that the two sides send delegations to Vienna in September to discuss the possibility of preventing the ''militarization of outer space.''
Inevitably, there was skepticism at the White House. The Soviets had been getting the worst of the propaganda exchanges, particularly since they walked out of all talks about both strategic and intermediate weapons last November. They, not Washington, had broken off the talks. In the continuing battle for the hearts and minds of Western Europe, the Soviets had lost an important round. So Moscow's new move on June 29 could be nothing more than an effort to regain lost propaganda ground.
And the propaganda battle has continued over whether the US reply accepting the Vienna meeting proposal had or had not included a ''precondition'' which the Soviets considered unacceptable. At this writing, Moscow was still asserting Washington had attached a ''precondition.'' In fact, Washington had not. It had indicated that it was interested more in the ''reduction of strategic and intermediate nuclear weapons'' than in outer space weapons.
But while Soviet Foreign Minister Andrei Gromyko was asserting that the US reply was ''totally unacceptable,'' an unnamed high Soviet expert in arms control was giving an interview to William Beecher, the Boston Globe's military correspondent, setting forth a new approach to the whole arms control problem. The Soviet expert said the new approach was being studied in some quarters in Moscow. He did not know whether it would be adopted, but it was being studied.
The most interesting feature of the plan as sketched out to Mr. Beecher was that it would lump together in new talks all types of nuclear weapons, including strategic (intercontinental) and intermediate (Euromissiles). The implication is that Moscow, having walked out of the separate talks for those two types of weapons, now is looking for a face-saving way of getting back.
Moscow has insisted so vehemently that it will not resume intermediate weapon (Euromissile) talks unless NATO withdraws its new missiles from Europe that these particular talks are widely considered to be dead. But under the new approach, the Soviets would not be returning to either the strategic or intermediate talks as such. They would be talking about those weapons in a new context.
Because the idea was contained in an interview with an American journalist, it was not official and could be repudiated. But ideas like that seldom get aired in Moscow without high authority. This looked like a trial balloon sent up to test reaction in Washington.
Arms control talks are unlikely to get anywhere unless both parties have their own reasons for being ready to work out a trade. It usually happens when there is a balanced desire on each side for some concession by the other. Does each have bargaining chips it is ready to spend for something it wants?
Today the United States has bargaining chips. Years of research and development are paying off. On June 10 an American antimissile missile successfully intercepted and destroyed an intercontinental ballistic missile in mid-flight in space. In November the US is planning to test an antisatellite weapon. Work is supposed to be well along on improving the accuracy of the nuclear missiles mounted on the US Navy's Trident submarines. The new technologies are moving from the drawing board to impressive performances.
The Soviets were uninterested in serious negotiations when they were, or seemed to be, moving ahead in weaponry faster than the US. But now the US seems to have the advantage in momentum. It can hardly have been pure coincidence that Soviet President Konstantin Chernenko called for a ban on antisatellite weapons on the day after the Pentagon disclosed the successful interception of the intercontinental ballistic missile.
But for Washington to be willing to trade there has to be something it wants from the Soviets. There is. Washington has always worried about the ''throw weight'' of the big Soviet SS-18 intercontinental ballistic missiles. Some of them throw a warhead with a 20-megaton charge. The American Trident C-4 missile is rated at 100 kilotons, or only one two-hundredth of the explosive force of the SS-18's charge.
The Soviet analyst who outlined his new ideas to Mr. Beecher of the Boston Globe said that in new negotiations it might be desirable to try to balance off different types of weapons against each other. The proximity of a NATO Pershing II, for example, might be balanced against the triple warheads of the SS-20 - or even, by implication, against the superblast of the SS-18. Then trading could begin.
What would the Soviets give up to induce the Americans to agree to a ban on weapons in outer space, and vice versa?
No one can know whether a trade is possible unless or until the delegations of experts sit down together and start trying to match each other's proposals. Could Washington be ready to do that by September? Is Moscow serious?
It would seem surprising for the Soviets to offer a meeting in September, which would be a political plus for Mr. Reagan in the American political campaign, unless they were serious or now assume Mr. Reagan is going to win anyway. Why would they give Mr. Reagan a gratuitous boost?
So, don't be surprised if serious rather than just propaganda talks get going in Vienna in September.