Not a big breakthrough. But not to be overlooked. That's the way Western Kremlin-watchers here in Moscow assess the possibility of a face-to-face meeting between President Reagan and Soviet Foreign Minister Andrei Gromyko.
Mr. Gromyko's senior assistant, first deputy foreign minister Georgi Kornyenko, indicated the Soviets would consider renewing Gromyko's practice of calling at the White House after he attends the opening of the United Nations General Assembly in New York later this month.
Gromyko has done that in previous years, and Mr. Kornyenko said that if Washington thinks ''it is appropriate to turn back to that practice, I believe there will be no difficulty on our part.''
Spokesmen at the State Department and the White House, and Western embassy sources here in Moscow, were quick to point out that no meeting had actually been scheduled. But one source said the idea of a meeting ''has been in the air'' for some time, and ''it will be considered.''
Why would Gromyko head for the White House, even while Moscow is apparently instructing the leaders of its East-bloc allies - such as East Germany's Erich Honecker and Bulgaria's Todor Zhivkov - to refrain from contacts with the West?
One obvious answer, according to some analysts here, is the degree of control that Moscow can exercise over such contacts. Another: The Soviets place much importance on superpower-to-superpower meetings, in which their status as a world power is explicitly recognized.
For those reasons, Gromyko may indeed be willing to meet not only with his American counterpart, United States Secretary of State George Shultz, but also with President Reagan.
But both countries obviously have one eye on the calendar. A meeting with Mr. Reagan just over a month before the US presidential election could yield pluses and minuses for both sides.
For Reagan, such a meeting might help convince the electorate that his administration is able to advance East-West relations - Democrats' charges to the contrary notwithstanding. If the meeting goes sour, however, Reagan might simply be able to point to it as yet another example of Soviet truculence - and his own ability to ''stand up'' to the USSR.
Gromyko might use such a meeting to assess how this country might deal with a second-term Reagan administration. Or, he might instead use the occasion to pummel Reagan publicly for alleged ''inflexibility'' or unreasonableness.
But a few analysts here in Moscow - still a decided minority - speculate that the first signs of a thaw may soon become apparent. Some, in fact, are linking the sudden removal of Soviet armed forces Chief of Staff Nikolai Ogarkov with a possible change in Kremlin tactics.
In their view, Marshal Ogarkov may have been ousted because he spearheaded the deployment of SS-20 missiles targeted against Western Europe. Those deployments sparked NATO to deploy its own new-generation nuclear missiles, a move that helped to plunge East-West relations to their current low point.
If this analysis is correct, a Gromyko trip to Washington might be yet another step in a gradual thaw in relations.
But Western diplomats here are cautious. They note that the Kremlin's rhetoric continues to be unremittingly hostile. They point to the cancellation of the Honecker and Zhivkov visits to West Germany. And they conclude that Moscow's future intentions are, as always, very much a matter of speculation.