So while other American religious groups, like the Episcopal Church, are tearing themselves apart over same-sex marriage, that front is relatively calm for Jews — who are, by contrast, exercised about intermarriage. For rabbis in particular, being pro-gay but unwilling to perform interfaith marriages is common.

Among Jews, the movement to sanctify same-sex relationships has moved quickly. In the Reconstructionist and Reform branches of American Judaism, it is now difficult to find a rabbi who will not do a same-sex wedding. In the centrist Conservative branch, there is no reliable count, but a growing number of rabbis perform such weddings. Only in Modern Orthodox and ultra-Orthodox communities, about 10 percent of all American Jews, do rabbis routinely refuse to do such ceremonies.

Although many Reform rabbis perform interfaith weddings, and the Reconstructionist seminary outside Philadelphia is considering lifting its ban on students’ being in relationships with non-Jews, many liberal rabbis will still not marry a Jew to a non-Jew. And the Rabbinical Assembly, the Conservative group, does not allow its members to perform such weddings. Which means that some rabbis who support gay rights must say no to gay or lesbian congregants’ weddings, if a non-Jew is involved.

“The comfort that I have working with L.G.B.T. families has predated the Conservative movement’s shift on the topic,” said Menachem Creditor, the rabbi of Netivot Shalom, in Berkeley, Calif., referring to lesbian, gay, bisexual, and transgender families. He said he had “a very hard time saying no to interfaith couples because the celebration of love is as holy as it gets.”

Interfaith couples often create richly Jewish homes and lives. But he feels bound by the constraints of the Conservative movement. “I believe in the process of gradual change that Conservative Judaism has always embraced,” Rabbi Creditor said.

He does try to recognize interfaith couples who attend his synagogue. Unlike many rabbis, he will invite them to come forward for an “aufruf,” the ceremony of blessing the Torah on the Sabbath before a wedding.

And while some congregations will not announce a member’s pending interfaith wedding in the monthly bulletin, Rabbi Creditor proclaims interfaith couples’ milestones, including anniversaries, “with the same language” used for couples who are both Jews.