In a break with 2,000 years of Jewish tradition, the top leader of Reform Judaism in North America has called for abolishing the principle that the Jewish identity of a child is determined solely by whether its mother is Jewish.

Rabbi Alexander Schindler, president of the Union of American Hebrew Congregations, in an address delivered to his organization's general assembly last night in Toronto, proposed changing Jewish law and practice to recognize fathers as well as mothers as transmitters of the Jewish heritage to their children.

"The status of Jew should be conferred on any child, either of whose parents is Jewish, provided they both agree to raise their child Jewishly and do so," Schindler declared.

Although there has been some discussion in scholarly circles of the problems this tradition has raised in modern society, Schindler's proposal for a formal study of it marks the first real effort to change it. Given the strong respect for tradition among Jews, such a change is expected to involve a fairly lengthy process of study and debate before a consensus can be reached.

Schindler's proposal strikes at the heart of one of the most perplexing questions in Judaism today, the issue of who is a Jew. Unlike religions such as Catholicism and Lutheranism, Judaism goes beyond a set of religious beliefs to include heritage. Many modern-day Jews, in fact, are not affiliated with synagogues.

Schindler pointed to one "dreadful anomaly" that results from the current tradition: "The offspring of a mixed marriage, whether reared as a Jew or not, is automatically a Jew so long as the mother is Jewish," he said.

"But if the mother is not, the offspring must ultimately undergo formal conversion, even if [the child] was raised as a Jew and lived in an intensely Jewish home," he said. The situation, he added, is "nonsensical, absurd."

The tradition, Schindler pointed out, causes particular problems in cultures like this one where "the Jewish intermarriage rate is approaching 40 percent," with the "preponderant majority" of mixed marriages involving Jewish men.

But Schindler anticipates the hurdles to changing the tradition. "A tradition spanning two millenia should not be altered lightly, I agree," he said in his address.

Unlike secular legal systems, there are not procedures for amending or repealing Jewish law and tradition.

In fact, Jews tend to respect tradition more than many ethnic or religious groups because it has helped preserve them as a people through periods of persecution.

To complicate matters further, the three major branches of Judaism -- of which the Reform movement is the most liberal -- do not share the same understanding of the ancient traditions.

Nevertheless, Reform Judaism has been known for its adaptations of ancient traditions to present-day circumstances.

In his remarks last night, Schindler asked his organization, which represents the lay leadership of Reform Jewry, to approve a resolution to "initiate a process of study and consideration with the Central Conference of Reform Rabbis" and the movement's scholarly arm, the Hebrew Union College.

Once the idea has been studied and received the general approval of these groups, individual rabbis and congregations within Reform Judaism could then begin to implement it.

Rabbi Wolfe Kelman of New York City, executive vice-president of the Rabbinical Assembly, the national organization of conservation rabbis, said there has been some interest in the question among Conservative Jews, the largest arm of Judaism in the United States.

He said that at the assembly's last meeting in January, there was some interest expressed in discussing the question, but not enough to schedule a conferece session on it.

Schindler noted that the tradition of passing the Jewish line through the mother grew out of a time when men had several wives "and the children of the various wives lived with their mother." It was reinforced centuries later when Jews were scattered to often hostile lands and Jewish women were raped during pogroms or other violent attacks.

"A compassionate law permitted them to rear their children Jewishly, though they could not know just who the father was," he said.

Kelman noted that the tradition is a particular problem in Israel today because of the "many, many Russian Jews that come to Israel with non-Jewish wives." Under the traditional law, their children would not be considered Jewish, thus depriving them of many advantages that Israel offers Jewish immigrants.

Under Israel's current political arrangements, no changes in Jewish practice initiated by either Reform or Conservative Jews would be recognized there. Because of political alliances, only Orthodox practices are recognized -- a sore point with Conservative and Reform Jews.

In his speech, Schindler noted that changing the tradition "is still another way to make certain that our grandchildren will be Jews, that they will remain a part of our community and share the destiny of this people Israel."

Schindler, who assumed the leadership of Reform Jewry in this country four years ago, has become something of an iconoclast. Just a year ago, he challenged another, less-entrenched tradition when he proposed that Jews abandon their long resistance to missionary efforts and actively seek converts to their faith. CAPTION: Picture, RABBI ALEXANDER SCHINDLER . . . opposes 'dreadful anomaly"