Although two rounds of U.S.-Soviet talks on reducing intermediate-range missiles in Europe have concluded with no visible progress, American officials say the negotiations are not stalled and that the initial discussions were essential in setting the stage for a September session that may register gains.

"Each side has had a large meal to digest," one official said in characterizing the opening round of talks Dec. 1 through March 16, when the United States laid out its proposal, and the just completed second round, May 20 to July 20, when the Soviets explained their position.

While official secrecy is being maintained, the Soviets are believed to have suggested a treaty under which each side would be required to limit its forces to 300 intermediate-range weapons in Europe by a specified date.

The talks in Geneva are officially called the Intermediate-range Nuclear Forces (INF) negotiations and deal with weapons with ranges of roughly 1,000 to 3,000 miles as compared with the ocean-spanning weapons that are the subject of the U.S.-Soviet strategic arms reductions talks, or START.

The INF talks are aimed at the nuclear arms race in Europe. That has become a political problem in the West, where there have been large demonstrations against the planned deployment of new U.S. missiles, and a military problem for the Kremlin, because the new American missiles could cut deeply into the Soviet lead in such weaponry.

Though the two sides clearly remain far apart, each has gone through the intellectual exercise of laying out its best arguments and hearing lively rebuttals, and each has even made minor adjustments. Without this basis, in the view of U.S. officials, there could be no future progress.

Officials here are reluctant to call themselves optimistic with respect to an eventual agreement, but there is a feeling that "maybe now we can make some progress" at the round set to begin Sept. 30.

President Reagan publicly put forward in general terms a so-called "zero-zero" proposal last November in which the United States would forgo the planned deployment, beginning late next year, of 572 new Pershing II and cruise missiles in Western Europe. The Soviets in turn would have to dismantle 600 intermediate-range missiles in the field that are capable of hitting Western Europe. The idea behind the U.S. proposal is to remove this Soviet edge.

President Leonid Brezhnev has basically rejected this proposal and spoken publicly in more general terms about a moratorium on adding new missiles while negotiations proceed, a tactic that would prevent the U.S. deployment. He has also talked of possible unilateral reductions of hundreds of unspecified missiles, which Americans say are the Soviets' old SS4 and SS5 weapons rather than the new and most threatening SS20s.

And Brezhnev has held out the possibility of no further deployments of the triple-warhead SS20s in the European parts of the Soviet Union, west of the Ural Mountains.

It is believed that in the talks the Soviets have also proposed including certain types of aircraft within their limit of 300 weapons a side. Under this formula, the Soviets could propose, for example, to limit to 300 the combined number of their SS20 missiles and Backfire bombers that are clearly within range of Western European targets.

The SS20 can hit targets up to 3,000 miles away. Previously the Soviets have only proposed restricting the SS20 deployments in the European part of their country west of the Ural mountains.

American officials, however, point out that the SS20 could reach NATO countries from well east of the Urals. If Moscow now proposes limiting all SS20s that can reach Western Europe, that could constitute a change.

The Backfire can reach targets even farther away, up to 4,000 miles and more if it is refueled in flight. The Soviets, therefore, may be proposing only to limit the number of these planes based in the European part of Soviet Russia.

It is known that the Soviets in their proposal are counting 162 British and French missiles--some submarine-based, some based on land and all capable of hitting the Soviet Union--as part of the 300 weapons that would be allowed the United States. This is an approach that the United States rejects.

The Soviets have also publicly called for counting American airplanes based in Europe that are capable of carrying atomic bombs to the Soviet Union. This, combined with the counting of French and British missiles, would appear to rule out any American deployment of the Pershing and cruise missiles while allowing the Soviets to retain their main new weapon, the SS20.

As one official put it, the opening Soviet position appears to amount to zero Pershing and cruise missiles with no appreciable constriction on the Russian SS20 force.

The Soviets now have about 315 new SS20s, two-thirds of them based in striking range of Western Europe while the others are presumably aimed at the People's Republic of China.

The Americans are known to reject the Soviet position on several counts. The Backfire, officials point out, could be quickly moved in a crisis to European airfields. The SS20, although harder to move, is also mobile, which explains why Reagan has called for dismantling all such weapons rather than just allowing Moscow to withdraw them to more distant locations.

As for counting the British and French forces, U.S. officials have said that those are sovereign forces of those countries, that the French are not even in the NATO military command structure and that, since the negotiations are between Washington and Moscow, the United States has no way to negotiate reductions in other nations' forces.

At best, they suggest, the Soviets are seeking equality with the combined forces of several countries and superiority over any individual country. The Soviets have argued that since all of these weapons can hit their homeland while their intermediate-range weapons cannot hit the United States, these weapons are subject to being counted.