As the official Soviet news media heap praise on President Leonid Brezhnev, who is about to turn 75, diplomats here say there can be little doubt of the birthday present he would most cherish:
An unequivocal sign that martial law in Poland is going to work.
The scant and inconclusive evidence at time of writing left the impression Mr. Brezhnev might or might not get this, but that it was highly unlikely the gift would arrive in time for his birthday celebration Dec. 19.
What will arrive in Moscow is a group of fellow Warsaw Pact leaders, although diplomats assume the busy master of martial law next door, Gen. Wojciech Jaruzelski, won't be among them. The leaders are sure to talk about Poland. Whether they will say anything about it for public consumption is less clear.
The Soviet Communist Party newspaper Pravda said in a brief commentary Dec. 16 that the Polish crackdown had given the Poles a chance to solve their own problems.
Soviet officials dearly hope this chance pans out, without the need for muscle from Moscow, especially at a time when the Kremlin is bidding for improved ties with the West.
In what some foreign analysts saw as further evidence of the importance the Soviets attach to that priority, Brezhnev issued Dec. 16 what was clearly intended as a leak-worthy ''letter'' to visiting US business magnate Armand Hammer. It was promptly leaked. The gist was that the Kremlin hoped for friendlier ties with Washington.
Yet one Western ambassador, reflecting the concern of many diplomats here, suggested privately that martial law might prove only ''the start of a process'' of resistance and reprisal that could draw in the Soviets.
(British news reports spoke of ''rumors'' that Soviet transport planes had landed in Warsaw overnight. But by the evening of Dec. 16, Western diplomats here said they had not confirmed this; they cautioned such planes would not necessarily carry military cargo.)
Polish, Soviet, and other East-bloc media, with a near monopoly on information in light of restrictions on Western reporters in Poland, continued to report general calm there.
But the reports Dec. 16 also said security forces had moved in to thwart strike attempts in the Baltic ports of Gdansk and Szczecin, as well as in the industrial town of Wroclaw. The Soviet news agency Tass had said late Dec. 15 that ''vigorous actions by the forces of public order'' had also been taken against a steelworks strike in the city of Katowice.
A trickle of Western news reports - citing Western diplomats or travelers from Poland - spoke of some incidents of violence. Details were sparse, but the reports said batons and water cannon had been used against opponents of martial law.
One Western businessman, who said he had visited southern Poland Dec. 15, was quoted as saying coal miners near Katowice had welded together steel drums at the entrance of their mine.
A dispatch carried by the British Broadcasting Corporation said Polish authorities were removing or painting over posters calling for a general strike on Dec. 19.
Diplomats stressed none of this amounted to evidence of mass resistance to the Polish crackdown, or of widespread violence. But the consensus was that, at a minimum, prospects for ultimate success or failure of martial law still hung in the balance.