A decision by Reform Jewish rabbis to recognize as Jewish all children of interfaith marriages involving a Jewish partner--instead of just the children of a Jewish mother--has been denounced by Orthodox rabbis as a threat to Jewish unity.

The (Reform) Central Conference of American Rabbis voted at a national convention in Los Angeles to recognize as Jews children born of a mixed marriage in which only the father is Jewish.

"The child of one Jewish parent is under the presumption of Jewish descent," the conference agreed. The decision means that a child born of a mixed marriage in which the father is Jewish does not have to "convert" to Judaism.

Traditional Jewish law recognizes as Jewish only the children born to a Jewish mother.

Reform rabbis said many of their colleagues already had been recognizing all children of a mixed marriage as Jews.

"It's (the decision) a tragedy," said Rabbi Gilbert Klaperman, president of the Rabbinical Council of America, the largest Orthodox rabbinical group in the world. "It will polarize the Jewish community to a point where the Orthodox will have to remove themselves from any contact with the Reform."

He said the decision places in jeopardy continued participation of the Orthodox rabbis in the Synagogue Council of America, an umbrella group of major Orthodox, Conservative and Reform bodies.

Christian and Jewish religious leaders are criticizing President Reagan for remarks made in an apparent attempt to counter support among U.S. religious groups for a nuclear freeze.

Reagan, speaking to the annual convention of the National Association of Evangelicals in Orlando, Fla., on March 8, urged "believers" to "speak out against those who would place the United States in a position of military inferiority." The 1,000 convention delegates debated the nuclear freeze issue but took no stand.

White House aides told reporters traveling with the president that his remarks were meant to stir opposition to the nuclear freeze being supported by some church leaders, particularly Roman Catholic bishops. The National Council of Churches, made up of Protestant and Orthodox churches, also has called for a nuclear freeze.

Rabbi Walter Wurzberger, president of the Synagogue Council of America, said the president had "every right" to oppose the freeze. But "he has no right to stigmatize those who disagree with his brand of 'civil religion' as succumbing to the 'temptation of pride' and seeking the 'illusion of peace,' " Wurzberger said. The council is an umbrella group of Orthodox, Conservative and Reform rabbis.

In a separate criticism, Orthodox Rabbi Gilbert Klaperman, president of the Rabbinical Council of America, accused Reagan of attempting to "polarize the different religious elements in America" and of suggesting that freeze advocates are "not loyal Christians."

Both Jewish organizations recently adopted strong antinuclear positions.

At a press conference of religious leaders at the Riverside Church in New York City, the Rev. William Sloane Coffin, pastor of the nondenominational church, condemned the "kind of self-righteousness exhibited by the president" in the speech before the evangelicals.

"What this country lacks is not patriotism on the part of the people, but humility on the part of its leaders," Coffin charged.

In a CBS News interview, the Rev. Harvey Cox, an American Baptist theologian at Harvard Divinity School, also criticized Reagan's remarks.

The head of a three-member delegation to the United States from a Protestant church council in Latin America called last week for the U.S. government to "get out of the struggle in Central America."

Methodist Bishop Federico Pagura of Argentina, president of the Latin American Council of Churches (CLAI), told reporters in New York that the result of U.S. support for "oppressive" regimes such as those in Guatemala and El Salvador and efforts to undermine the left-wing Nicaraguan government has been "mass killings."