New Jersey Gov. Jon S. Corzine on Thursday signed a civil unions law giving gay couples all the rights and responsibilities — but not the title — of marriage.

The law makes New Jersey the third in the nation to institute civil unions and the fifth to offer same-sex couples some version of marriage. Connecticut and Vermont allow civil unions for gay couples. Massachusetts allows gay couples to marry; California has domestic partnerships that bring full marriage rights.

"We must recognize that many gay and lesbian couples in New Jersey are in committed relationships and deserve the same benefits and rights as every other family in this state," Corzine said. About 150 people attended the bill signing.

The New Jersey law takes effect Feb. 19. Same-sex couples seeking civil unions will have to wait for three days for a ceremony to take place after registering their plans with local officials. That is the same waiting period for couples seeking marriage licenses.

Once joined in civil union, gay couples will enjoy adoption, inheritance, hospital visitation, medical decision-making and alimony rights and the right not to testify against a partner in court.

"I believe very fundamentally in equal protection under the law and this legislation is about meeting that basic responsibility and honoring the commitments that individuals have made to each other," said Corzine, a Democrat.

The law passed the Legislature on Dec. 14 in response to an October state Supreme Court order that gay couples be granted the same rights as married couples. The court gave lawmakers six months to act but left it to them to decide whether to call it unions "marriage" or another term.

Gay couples have welcomed the new law, but argue not calling it "marriage" creates a different, inferior institution. Even some same-sex couples who attended the bill signing remained lukewarm about the law.

"It's a step forward, but it's not true equality," said Veronica Hoff, 52, of Mount Laurel, as she stood with her partner.

Social conservative groups and some lawmakers opposed the measure, reasoning it brings gay relationships too close to marriage, but it easily passed the Legislature.

"It's same-sex marriage without the title," said John Tomicki, president of the New Jersey Coalition to Preserve and Protect Marriage. "It uproots the cardinal values of our culture."

He said opponents would push for a constitutional amendment that would ban same-sex unions in New Jersey, no matter what they're called.

"Let the voters decide that marriage is defined as a union of one man and one woman," Tomicki said.

Democrats who control the Legislature have said they have no plans to consider such a proposal.