The change involves just a few words in the law and would affect a half-dozen people a year.

But indications that Israel is about to change its Law of Return to deny automatic citizenship to non-Orthodox converts have generated enormous controversy among American Jews, most of whom are Reform or Conservative.At issue, they say, is whether these branches of Judaism are perceived as legitimate. At risk, they say, is the unified support of American Jewry that has sustained Israel through four wars and scores of crises.

American Jewish efforts on behalf of Israel "are going to be subordinated to the effort to get this changed. Israel is going to be the object of a crusade in which they're going to be the bad guys, not the good guys," said Rabbi Eric Yoffie, executive director of the Association of Reform Zionists of America.

Twenty-seven organizations - among them the American Jewish Congress, the American Jewish Committee, B'nai B'rith, Hadassah and all major Reform and Conservative governing bodies - issued a statement Nov. 12 warning of the "enormous damage, actual and symbolic" to Jews living outside of Israel.

The vast majority of Jews worldwide are non-Orthodox, even in Israel.

The Council of Jewish Federations, which will raise an estimated $850 million this year for Jewish needs around the world, said it would dispatch a delegation to Israel to lobby against the change.

"We are dealing with the perceived disenfranchisement of millions of American Jews who will feel they have been written out," said Shoshana S. Cardin, past president of the council.

Under Israeli law as it stands, all Jews - defined as the children of a Jewish woman, or converts - are automatically accepted as Israeli citizens.

For decades, ultra-Orthodox elements in Israel have sought to change the law so that only those who are converted "in accordance with Halacha" - the strict, Orthodox interpretation of Jewish law - are eligible.

Support for the Orthodox religious parties doubled in this year's parliamentary elections. Though that amounted to only 18 seats in the 120-seat Knesset, it gave the religious parties enough votes to give either the Labor or Likud blocs the majority needed to form the next government.

Last week it was reported that the religious parties had agreed to support Likud and had won numerous concessions, including a promise to seek a change in the Law of Return.

Unless Labor and Likud agree to form another unity government, U.S. Jewish leaders fear, the change is inevitable.