(AP) HARRISBURG, Pa. The state Senate on Wednesday approved a proposed constitutional amendment that would echo state law in seeking to outlaw gay marriage in Pennsylvania, and narrowly rejected efforts by conservatives to include a companion ban on civil unions.

The push for the legislation is a last-ditch effort by supporters to keep alive the possibility for a statewide referendum as early as 2007 on a constitutional amendment to ban gay marriage.

With differences on the issue between the House and Senate, the multiyear process that is required to amend the state constitution could be set back two years if the chambers do not agree before lawmakers take a vacation from Harrisburg in July and August.

The bill passed, 38-12, but was a bitter pill for conservatives who had also sought a ban on civil unions, which they see as tantamount to gay marriage. An effort to add a ban on the “functional equivalent” of marriage to the legislation divided the Republican majority and failed, 23-27.

Sen. Jane Orie, R-Allegheny, said that a vote against wider legislation to ban gay marriage as well as civil unions was “a vote against marriage in Pennsylvania.”

She and other Republicans warned that, without a constitutional amendment, a state judge could act on a legal challenge to Pennsylvania law and effectively legalize gay marriage or civil unions between gays. The House on June 6 approved a proposed constitutional amendment to define marriage as being between one man and one woman and to prohibit civil unions between gays by banning “a legal union identical or substantially equivalent to that of marriage for unmarried individuals.”

Liberal opponents characterized a ban similar to the kind of racial discrimination that courts have struck down in previous decades. Other opponents questioned the need for a constitutional amendment to guard against a hypothetical challenge to a 1996 state law that already defines marriage as between a man and a woman.

“This measure is disheartening, it is divisive, and it is diversionary to say the least,” said Sen. Jim Ferlo, D-Allegheny. “The Pennsylvania Constitution should not be tarnished with this measure.”

In addition, opponents contended that civil unions have nothing to do with marriage, and said a ban would simply take away rights and benefits from gays and many other classes of people who live together, but are not married.

“If we’re concerned about the sanctity of marriage, I don’t know how it hurts your marriage ... if some gay couple in Philadelphia is living together,” said Sen. Vincent J. Fumo, D-Philadelphia. “Mind your own business, stay out of the bedroom.”

Gay marriage has re-emerged as a major election-year issue, as six states are scheduled for a referendum on a constitutional ban on gay marriages. Twenty states have adopted constitutional definitions outlawing gay marriage, with more than half extending the ban to civil unions.

Amending the Pennsylvania Constitution requires the approval by the House and Senate in two successive two-year sessions of the General Assembly and then the approval of voters in a statewide referendum.

Constitutionally, any such legislation must be approved by both chambers three months before the Nov. 7 general election if the process is to continue into the 2007-08 session of the General Assembly. That would make Aug. 7 the deadline for the House and Senate to agree on an identical legislation, but the chambers are scheduled to leave Harrisburg at the end of next week to take a summer vacation that lasts into September.