OLYMPIA, Wash. (AP) — A referendum seeking to overturn an "everything but marriage" bill for same-sex couples was filed Monday by opponents who want voters to reject the latest effort to expand the state's domestic partnership law.

Referendum 71 was filed by Larry Stickney, president of the Washington Values Alliance. Supporters need to get more than 120,500 valid voter signatures by July 25 in order to qualify for the November ballot.

Stickney said he was filing the referendum on behalf of a broad-based coalition, saying that foes were going to "do all we can to turn this back."

Gov. Chris Gregoire said she will sign the domestic partnership expansion into law on May 18, saying it "embraces the values of the people of the state of Washington."

"Everyone in this state should be treated equally," she said.

Gregoire called the referendum effort "unfortunate" and said she would campaign against it if it makes it to the ballot.

The filing of the referendum delays the scheduled July 26 effective date of the law until the signatures are counted. If opponents qualify for the ballot, the law is delayed until the results of the November election.

The bill expands on previous Washington state domestic partnership laws by adding such partnerships to all remaining areas of state law where currently only married couples are mentioned. The statutes range from labor and employment rights to pensions and other public employee benefits.

The underlying domestic partnership law, which Sen. Ed Murray, D-Seattle, spearheaded two years ago, provided hospital visitation rights, the ability to authorize autopsies and organ donations, and inheritance rights when there is no will.

Last year, lawmakers expanded that law to give domestic partners standing under laws covering probate and trusts, community property and guardianship.

"While it's regrettable that a referendum is being filed to undo the progress we made this session to treat gay and lesbian families the same as married families, I don't believe that voters will decide in November to take away rights from anyone," Murray said in a statement e-mailed to reporters Monday.

As of Monday, more than 5,300 domestic partnership registrations had been filed in Washington since July 2007.

Stickney said that opponents to the law worry that it will ultimately lead to courts legalizing same-sex marriage in the state.

"This kind of legislation kind of tees it up for the courts to act," he said.

Four states have legalized same-sex marriage: Connecticut, Massachusetts and Iowa through court order, and Vermont through legislative action.

Same-sex marriage was legal in California for five months until a state referendum to ban it passed last fall.

Bills to allow same-sex marriage are currently before lawmakers in New Hampshire, Maine, New York and New Jersey.

New Jersey, California, New Hampshire, Oregon, Washington and the District of Columbia have laws that either recognize civil unions or domestic partnerships that afford same-sex couples similar rights to marriage. Thirty states have gay marriage bans in their constitutions.

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The domestic partnership bill is Senate Bill 5688.