Poland's communist authorities and the independent trade union federation Solidarity are locked in the most dangerous round of brinkmanship since the union was formed seven months ago.

The issues at stake in Poland's latest crisis go much deeper than the violence in the northern town of Bydgoszcz, where police evicted Solidarity activists from a local assembly meeting. Both sides appear to believe they are defending the basic principles of their existence: the government's right to govern and the union's right to security for its members.

If no compromise is reached before next Tuesday -- and the room for maneuver seems agonizingly narrow -- an indefinite general strike will go ahead in all of Poland. There would then be a very real possibility that neither the government nor Solidarity would survive intact in their present form. A Soviet intervention, still unlikely, cannot be ruled out.

This is taking place just six weeks after the fornation of a new government, headed by Gen. Wojciech Jaruzelski, brought many high hope that the crisis would be resolved.

The one chink of light on this otherwise bleak landscape is the fact that there are responsible people on both sides who have much to lose -- and nothing to gain -- by total confrontation. The stark alternative between compromise and anarchy is itself a source of enormous pressure on Poland's leaders to reach a sensible solution.

Both Communist Party leader Stanislaw Kania and Jaruzelski have staked their reputations on resolving Poland's problems by negotiation rather than by conflict -- and without external intervention. Both men have a background of responsibility for security and understand, perhaps better than anyone else in Poland, the unforeseeable consequences of any resort to force.

On Solidarity's side, Lech Walesa has tried desperately in the last week to head off the threat of a general strike. After years of underground struggle for the cause of independent trade unions, he knows how much Solidarity has gained since last summer. He also realizes that it is foolish to risk everything by demanding too much at once.

Finally, there is the Catholic Church, which takes the long view of Polish history and has a vested interest in preserving the country's independence. At previous time of crisis, the primate of Poland, Cardinal Stefan Wyszynski, has acted as a tructed mediator between government and unions. His role could be crucial in any settlement to the present crisis.

The question to be answered in the next few days is whether these leaders are still capable of imposing their will on events -- or whether the forces in Poland favoring confrontation have become irresistable.

The speed with which the crisis has blown up proves that the basic contradiction in attempting to marry independent unions to a one-party state has not been resolved by the appointment of an Army general as premier. In a pluralistic society, disputes of this kind are inevitable, but Poland lacks respected democratic institutions and legal mechanisms to defuse them peacefully.

Each side sees sinister forces at work in the other camp. Solidarity's interpretation of last week's violence in Bydgoszcz is that it was provoked by hard-liners within the state bureaucracy opposed to the conciliatory policies of Kania and Jaruzelski. Tens of thousands of predominantly midlevel bureaucrats, so this argument runs, are prepared to go to any lengths to hold onto their jobs and privileges.

The government's view was expressed yesterday by Deputy Premier Mieczyslaw Rakowski in talks with Walesa. He accused influential elements in Solidarity of wanting to wage "a holy war" against the communist authorities. As evidence, officials point to resolutions by some Solidarity branches insisting that about 1 million Communists who also belong to the union decide finally which side of the fence they are on.

In the background is the Soviet Union, which since last month's Soviet Union, which since last month's Soviet Communist Party congress, has been exerting increasing pressure on the Polish leadership to take a tougher line with Solidarity. A commuique issued after the Moscow summit of Polish and Soviet leaders made it plain that the Kremlin expected decisive action to restore the government's authority.

Given this background, it was more or less inevitable that the Warsaw authorities would have to support the action of the Bydgoszcz police against approximately 30 Solidarity members a week ago. Much remains unexplained about the affair, including whether the Solidarity activists were planning to occupy the city assembly -- as the government claims -- or had merely come to hold already-scheduled talks with local officials, as union leaders say.

The most controversial confrontation took place outside the assembly hall when, according to the union's version, the Solidarity activists were punched and pummeled by police. Three union activists had to be taken to hospital with serious injuries.

Solidarity claims this was only the latest in a long line of beatings of union activists in many parts of Poland. In most cases, the assailants were not identifiable -- but on this occasion they wore police uniforms. Since one of the basic provisions of the Gdansk agreement that recognized Polish workers' right to form independent unions was the guarantee of security for union members, Solidarity demanded that those responsible for the violence be punished.

For its part, the government says it is unclear how the Solidarity members were injured. A preliminary report on the affair said there was no violence inside the hall.

Once again, Solidarity and the communist authorities are engaged in a test of wills, the outcome of which will be determined not by simple moral categories, but by their respective power.

There have been similar contests in the past, notably over Solidarity's legal registration last November and over work-free Saturdays last January. This time the stakes are higher, however, and each side is probably more internally divided than ever before.

The latest trial of strength comes at a time of overt pressure from outside in the form of Warsaw Pact maneuvers that apparently have been extended longer than planned. Moreover, the economic situation in the country is increasingly desperate, with the government claiming that food supplies would last for only 12 days in the event of a strike.

Public support for Solidarity appears to have waned because of continuing instability and growing economic problems. But the authorities might be making a great mistake if they interpret this as an opportunity to get the union on the defensive. In any final showdown, the sympathy of a vast majority of Poles would probably still remain with Solidarity.

On the other side, the communist leadership has come under fire from its own ranks. Reform-minded Communists have accused hard-liners in the party of having no idea of how to deal with the country's crisis.

If a planned four-hour nationwide "warning strike" goes ahead on Friday, it will seve to reveal the extent of Solidarity's support. The communist authorities, meanwhile, are attempting to mobilize their supporters by calling plenary sessions of the party's Central Committee and the parliament on Sunday and Monday.

The paradox of Poland's efforst at democratization is that only by looking disaster in the face can the country retreat from it. This has encouraged brinkmanship on both sides. The tragedy is that, in testing each other's nerves, everybody could fall over the precipice.