The world focused attention this week on the battle of wills between Poland's communist authorities and the independent trade union federation Solidarity. But in the shadows of that contest, an equally important struggle has been taking place within the ruling Communist Party.

The political power play is likely to culminate Sunday in a plenary session of the party's Central Committee. The outcome could be crucial for the country's future.

The week began with a serious setback for the moderates in the Polish leadership who are represented by party chief Stanislaw Kania and the prime minister, Gen. Wojciech Juruzelski. Their policy of settling all disputes through a constant dialogue with society appeared to be jeopardized by Solidarity's sharp reaction to alleged police brutality in the northern city of Bydgoszcz and the attempt by hard-liners to engineer a final showdown with the union.

By the end of the week, commited reformists in the party were becoming much more assertive and it even appeared as if they might be getting the upper hand.

The week's developments illustrate an underlying theme to the Polish crisis: the strong resistance of a significant section of the state bureaucracy to reforms. This intraparty feud, combined with pressure from Poland's Soviet Bloc neighbors, has vastly complicated Kania's attempts to build a new, more stable national consensus between rulers and ruled.

Solidarity's interpretation of events, which is now accepted by most Poles, is that the violence in Bydgoszcz was provoked by hard-liners in the state security in the hope that it would produce an angry union backlash while joint Warsaw Pact maneuvers were taking place in Poland.

The incident came at a propitious moment for conservatives in the leadership who are widely believed to be grouped around the Politburo member in charge of ideology and propaganda, Stefan Olszowski.

Olszowski has been identified by Western observers with the reformist wing of the Polish leadership largely because of his outspoken opposition to the former party leader, Edward Gierek. But in ideological and political matters, he has taken a distinctly conservative stance.

Last Sunday, the ruling Politburo held a special session that ended with a tough statement totally exonerating the Bydgoszcz police, accusing Solidarity of attempting to create anarchy, and instructing Poland's 3 million communists not to take part in "strikes of a political character."

The tough line was prompty endorsed by Moscow and other Soviet bloc countries. It was accompanied by a propaganda campaign seeking to put the blame for the Bydgoszcz affair solely on the union.

In order to recover their position, the moderates in the leadership needed time to demonstrate the overwhelming support in the country at large for a compromise solution. It was in order to give them this breathing space that Solidarity's leader, Lech Wallesa, argued so hard in favor of postponing the threat of an indefinite general strike until next week.

On Thursday, Jaruzelski met with the head of Poland's Roman Catholic Church, Cardinal Stefan Wyszynski. They agreed on the need for the full facts of the Bydgoszcz affair to be brought to light.

Kania, meanwhile, called in news media chiefs to remind them that the party's policy on the need to resolve conflictss exclusively by political means remained unchanged.As a result of this meeting, television and the press started giving much more attention to Solidarity's point of view.

Finally, there was a flood of resolutions from basic party organizations around the country, mostly urging that the deadlock be ended through compromise.

On Friday, the almost complete success of the four-hour "warning strike" demonstrated that, in the event of a final showdown, the vast majority of Poles would support Solidarity. Despite the Politburo's instructions, many ordinary party members also took part in the strike.

On the eve of the Central Committee meeting, it is clear that the hard-liners cannot hope to govern the country in opposition to the wishes of 90 percent of society -- and perhaps even a majority of Polish communists themselves. In a newspaper interview, Deputy Premier Mieczyslaw Rakowski conceded that one of the major obstacles to stability in Poland was "the psychological conditioning of a portion of officialdom." He balanced this by accusing some Solidarity members of "extremism and irresponsibility."

Solidarity members on the Warsaw daily Zycie Warszawy put it more bluntly when they said in a statement printed by the paper that some people in power saw the process of renewal as a threat to their own careers. "Byddgoszcz has demonostrated that these people want to push the country to the brink of an abyss. They are prepared to employ all available means, even if that entails a tragic confrontation, to retain their influence and positions," they wrote.

It will be difficult for the Central Committee to ignore this groundswell of public opinion -- even though most of its members could hardly be described as reformists themselves. At the same time they are faced with an increasing pressure from their Warsaw Pact allies to hold firm against Solidarity's demands.

The events of the past week have proved that Solidarity is prepared to go to any lengths to defend what it regards as its gains. Attempts to push the union back, using political means in Poland, seem certain to fail. That leaves the Kremlin with the alternative of either using its own troops, with all the risks and uncertainties that would entail, or tolerating the conciliatory policies of the present Polish leadership