THE AGREEMENT reached between strikers in Gdansk and Szczecin and the government opens a second and more dangerous phase of the Polish crisis. In the first phase, the Kremlin stayed cool and kept its counsel to the Poles private, although it obviously opposed the whole notion of workers' independently pressing political as well as economic demands and of officials' consenting to bargain -- publicly yet -- with them. From the promptness and sharpness of its comment on the new agreement, however, it is evident that the Kremlin feels the Polish authorities have gone too far.

The gist of Moscow's comment is that the agreement endangers socialism in Poland. By the "Brezhnev doctrine," the Soviet Union arrogantly claims a right to intervene when it feels a fellow communist regime is threatened. (Why, by the way, did Douglas Fraser choose to tell Fraser choose to tell now of the United Auto Workers' token financial aid to Polish strikers -- a boast playing into Soviet efforts to blame the unrest on foreigners?) By the realities of geopolitics, the Soviet Union is in a position to intervene in Poland -- though, of course, at a cost. The question now is whether it will.

This is no time for coyness -- or complacency: the men in the Kremlin are who they are. They are not going to ignore the dizzying of the new agreement just because Westerners, meaning to be helpful to the Poles, paint it as a courageous exercise in democratizing socialism. The agreement undercuts the premise of Communist Party legitimacy, the party's claim to be the sole authentic representative of the working class, by accepting a new structure of non-party "self-governing" unions. The realm in which the new unions can "publicly express an opion." moreover, extends beyond bread-and-butter issues into large political matters like the division of national income between consumption and investment. The promise of a relaxation of censorship and of limits on arbitrary political arrest point toward a measure of political diversity unknow anywhere in the Soviet bloc. That the strikers also promise to eschew a political role, accept Communist Party leadership and hew to socialism is not likely to make the agreement more palatable to Soviet leaders. They know trouble when they see it.

Protest in Poland, it has been said, moves on a scale from bread to freedom to Katyn -- a reference to the Soviet army's massacre of some 4,000 captured Polish officers in 1940 during the period of the Stalin-Hitler pact. Polish nationalism, sharpened on antagonism to the Soviet Union and to Czarist Russia before that, remains a powerful force. It is indicative that after government negotiators and strike leaders signed their historic agreement on Sunday, they joined in singing the Polish national anthem. In setting its policy from here on in, the Kremlin must consider many factors, not least the high certainty that if the Red Army tried to impose control, Poles -- workers, officials, soldiers -- would fight back.