The Soviet Union - apparently surprised and angered by the degree of Western unity over the Polish crisis - is escalating its bid to convince Western Europe of the political and economic dangers of falling in with United States policy.
The Soviet strategy has become clearer on the heels of a meeting of the European Community and a subsequent, Jan. 11, session of the NATO foreign ministers on the Polish situation. Both gatherings produced a far higher degree of Western unity than the official Soviet news media had been predicting.
One reason for this, some diplomats here suggest, is that the Reagan administration has so far avoided pressing Western Europe to match US economic sanctions against Moscow move for move, and has pledged to continue arms talks with the Soviet Union.
Against this background, a Jan. 12 commentary by the Soviet news agency Tass in effect charged Mr. Reagan with plans to undermine arms talks without calling them off completely.
Dealing specifically with the superpower negotiations on nuclear forces in Europe, which resumed Jan. 12 after an agreed recess, the commentary said: ''The point in question is not only that the US consent to sit down again to talks . . . (but also) the goodwill of the US side and its readiness to work for agreements. . . .
''There are good reasons to think that, by artificially whipping up hysteria over the events in Poland, Washington . . . is preparing the ground for torpedoing the Soviet-American talks on nuclear arms in Europe.''
On the economic front, Moscow has suggested that the West Europeans stand to lose as much as the Soviet Union by any imposition of trade sanctions over the Polish crisis.
In a Jan. 9 Pravda article, the Soviet minister of foreign trade said expanding commerce with Western Europe met the Europeans' ''vital interests, particularly under conditions of economic recession. . . .
''Those countries which give in to pressure exerted from the other side of the (Atlantic) ocean may pay for this with the loss of their position in our foreign trade,'' he warned.
The point is not likely to be lost on Europeans. America's allies still seem unlikely to impose major trade sanctions over the crisis in Poland, short of Soviet military intervention there. Plans for a multibillion-dollar project to pipe Siberian natural gas to West Europe, for instance, seem in no immediate danger.
But at their recent meeting, EC ministers did pledge not to undermine unilateral US trade restrictions. This pledge, if fulfilled, seems likely at least to complicate the pipeline scheme, and conceivably, other projects.
The NATO session Jan. 11 made a similar pledge, but went further. All alliance members but Greece joined in saying they would consider economic and other measures against the Soviets, should martial law in Poland continue unabated.
Even if these are ''mere words,'' one foreign analyst here remarked, ''they are not words that can much please Moscow.''
The NATO and EC stands are seen as at least a temporary setback to Soviet hopes that general Western interest in - and rancor over - the Polish crackdown will subside quickly. The Western response could also bode ill for evident Kremlin hopes that the Europeans will press Washington for early concessions at the arms-control table.
In this context, the Soviet and Polish foreign ministers Jan. 12 wrapped up their countries' first formal talks since the imposition of martial law in Poland.
A communique at the end of the Moscow talks recorded joint condemnation of the EC and NATO statements. The document also contained the closest thing yet to a Soviet vote of confidence in the martial law regime - but was acrobatically phrased to omit reference either to martial law or to the Polish regime.
''The conviction was expressed,'' the communique said, ''that the Polish People's Republic . . . will, with the assistance of its friends and allies, cope successfully'' with its difficulties.