HONOLULU — Hawaii, the state that adopted the nation's first "defense of marriage" constitutional amendment a decade ago, has now become the latest battleground in the fight for same-sex civil unions.

It would become the fifth state to legalize the alternative to gay marriage if the Democrat-dominated Legislature and Republican governor approve a civil union law. The measure was passed by the state House this month but it now faces the Senate, where a divided committee is to vote Tuesday.

Republican Gov. Linda Lingle has declined to comment on the issue and it's unclear whether she would veto the bill.

Gay rights organizations argue that civil unions would promote basic equality in the nation's most ethnically diverse state, but opponents fear the erosion of an island culture that values conventional family ties.

"Society in general is becoming more accepting," said Suzanne King, a real estate office manager who is raising her 9-year-old daughter, Shylar Young, with her partner of nearly 28 years, Tambry Young. "It's not unusual to come upon a gay family. There isn't this fear that by giving us rights, it's going to reduce the traditional family."

King and Young said they want a civil union law so gay couples can more easily adopt children, share health benefits and gain hospital visitation rights. They plan to enter into a civil union if the measure becomes law.

Religious groups have been taking out newspaper ads, setting up Web sites and holding rallies urging lawmakers to preserve traditional marriage.

One anti-gay Web site includes photos of two men kissing each other and others apparently in gay pride parades. It warns of a bad influence on Hawaii "keiki," the Hawaiian word for children.

The LDS Church, which campaigned in California last year for a gay marriage ban, has not openly rallied opposition to civil unions in Hawaii this year. But some members of the Church of Jesus Christ of Latter-day Saints have been sharing e-mails urging people to calls their legislators opposing the bill.

"In Hawaii, people still believe in traditional marriage and the sanctity of marriage," said Dennis Arakaki, executive director of the Hawaii Family Forum, which also represents the Hawaii Catholic Conference. "There's no indication that values or perspectives have changed."

Only Massachusetts and Connecticut allow gay marriage, while Vermont, Connecticut, New Jersey and New Hampshire allow civil unions. Californians voted in November to overturn a court ruling that allowed gay marriage, but the state still offers domestic partnerships that guarantee the same rights as marriage.