Steel ring tightens around embattled Poland; Quandary for Kania: How to keep both the kremlin and his own workers happy?

The key question in the Polish cris is this: Will Polish party leader Stanislaw Kania and his new team be able to satisfy the conflicting demands of the Kremlin and the Polish workers?

The crisis is of far more than local importance. In Poland today, Moscow is face with the biggest grass-roots anticommunist workers' movement that the Soviet empire has seen since its expansion into Europe at the end of World War II.

If the movement is not contained, it could soon undermine the principle guaranteeing Moscow's ultimate control over its entire empire from the Elbe to the Pacific. This principle dictates that the Communist Party shall have absolute control over every activity vital to the running of the state.

Mr Kania is aware of all this. He knows how much is at stake for the Soviet leaders as well as himself and how Poland once again is a pawn in a much bigger game. Hence the anguish in the opening words of the statment from the Polish Communist Party's Central Committee Dec. 4:

"Countrymen, the fate of the nation and the country hang in the balance. . . . Continuing unrest is leading our homeland to the brink of economic and moral destruction."

Underlinign this public expression of anxiety was an almost simultaneous statement from the National Military Council. It asserted that the present situation was a considerable threat to the functiong of the state and could ultimately affect its defense potential.

But Mr. Kania and his military men are struggling with a dilemma:

* If the Polish party leaders fail to satisfy Moscow of their ability to assert authority, the Kremlin is likely to enforce its will by ordering Soviet tanks to roll.

* YEt, if the Polish leaders fail to satisfy their workers, the prospect is for more strikes leading toward deeper economic and political chaos -- which could also bring in the Soviet tanks.

Mr. Kania knows that the one thing the Soviet leaders cannot permit is an unraveling of communist power in Poland that might be the beginning of the collapse of the entire Soviet empire in Europe and beyond.

Soviet President Leonid Brezhnev has been relatively restrained since the crisis began in the summer. But there are signs that Soviet tolerance may be nearing its limit -- which is why such firm warnings against Soviet intervention have come this week from both the White House and the State Department in Washington.

But more than outside warnings, within Poland two things are immediately needed to head off Soviet military action:

1. Party leader Kania must somehow establish an image of his party's having regained control -- after retreating from July onward before the increasingly militant workers, now organized in free trade unions of which the biggest in Solidarity.

2. Solidarity's members -- particularly the younger ones -- must be persuaded to temper their apetite for further immediate political victories at the expense of the party and to concentrate instead on economic issues.

More than any of the other communist countries of Eastern Europe, Poland is on the edge of an economic abyss. It is massively in debt. It is short of food , partly because of two successive poor harvests. And its productivity rate continues to slump, partly because of work habits and partly because members of the free trade unions have so often resorted to strikes in recent months to back their increasingly political demands.

Solidarity leader Lech Walesa understands that for Poland's well-being, wildcat strikes must come to a halt. He has been trying to communicate this to his fellow workers. He has the backing of the leadership of the all-important Roman Catholic Church in Poland, for centuries seen as the guardian of Polish nationalism.

But this still leaves him with the Problem of persuading the roused activists within Solidarity that: (1) he is not sellling out to the Communist Party; and ( 2) by pressing for everything they want immediately, they risk losing all their gains of recent months.

The challenge is no less daunting for party leader Kania. He has this week carried out the fourth major change at the top level of the party since the crisis began. The latest change seems to have been effected to give him a team with which he can try to restore the party's credibility and authority.

The four last hard-liners at the top have been dropped. They were men who have been opposed to compromise with the workers from the start and who have sniped at Mr. Kania for his pragmatism. In some ways balancing their removal, there has returned to the Politburo the law-and-order figure of Gen. Mieczyslaw Moczar, who was minister of the interior a decade ago.

To many, General Moczar is a controversial figure with authoritarian tendencies. But his strength in the present situation is that to the mass of Poles he is a Polish nationalist first and a communist second. If he can help Mr. Kania win a similar image for himself, the party leader would have much stronger credentials for dealing with the workers and persuading them to accept compromise. If at the same time General Moczar's law-and-order reputation reasures the Kremlin, so much the better.

There can hardly be a single Pole, noncommunist or communist, who wants Soviet tanks lumbering down their streets against Polish workers. Paradoxically , the Soviet leaders are probably almost as reluctant as the Poles themselves to see this happen. But there is no doubt that if the Kremlin has to choose between military action and doing nothing while its empire disintegrates, it will choose military action.

Obviously, Moscow is going to draw the line somewhere -- and everything points to events being very close to that line.

The Kremlin has everything in place on Poland's borders for military intervention by Soviet troops (and perhaps other Warsaw Pact forces) the moment the word is given. Soviet troops are in any case already stationed in Poland as part of the Warsaw Pact's security arrangements.

Reluctance to order the tanks to roll prev sumably stems largely from recognition in the Kremlin that Soviet military intervention in Poland might well prove counterproductive in the long run.

It could silence for a time such voices as those of Solidarity leader Walesa, and of members of his organization more impatient and intemperate than he. But this could be achieved probably only after bitter fighting.In addition, Moscow would thereafter have to shoulder alone the burden of Poland's debts and economic plight.

On the world stage, Soviet Military repression of the Polish workers would demolish whatever remains to detente with the West, as US and other Western spokesmen are making clear.