OLYMPIA — Supporters of gay marriage in Washington said Monday they raised more than $952,000 last month for the campaign to uphold the state's new law, which is on hold pending the outcome of a November ballot measure.

The announcement by Washington United for Marriage comes a day before a deadline for initiative campaigns to file their monthly campaign-finance reports with the state Public Disclosure Commission.

"We want to continue this incredible momentum and ride this wave throughout summer to be competitive in the fall," said Zach Silk, the group's campaign manager. Silk said the campaign expects a fundraising spike by opponents later in the fall.

"We can't take anything for granted," he said.

Among the donations were $100,000 each from Microsoft CEO Steve Ballmer and co-founder Bill Gates.

Referendum 74 was certified for the ballot last month after gay-marriage opponents turned in more than 240,000 signatures, far more than the minimum of 120,577 valid voter signatures required.

The referendum seeks to overturn the law passed by the Legislature and signed by Gov. Chris Gregoire earlier this year. The law was supposed to take effect June 7 but was put on hold once the signatures were turned in.

Voters will be asked to vote "yes" to uphold the gay-marriage law or "no" to overturn it.

As of Monday, Washington United for Marriage said it had raised more than $2 million for the campaign to fight overturning the law.

Preserve Marriage Washington, which collected the signatures to put R-74 on the ballot, has raised more than $135,000, according to the most recent numbers with the Public Disclosure Commission, though it hasn't yet submitted totals for June.

The Washington, D.C.-based National Organization for Marriage, which was involved in ballot measures that overturned same-sex marriage in California and Maine, has said it will fight to strike down the law and has loaned regional coordinator Christopher Plante to the local campaign.

"We expect to be outspent on this," said Plante, now serving as deputy campaign manager for Preserve Marriage. "As the campaign goes on, sufficient funds will come to get this done and voters will bring us the rest of the way there."

Plante said that they ultimately hope to raise about $4 million.

Same-sex marriage is legal in New York, Connecticut, Iowa, Massachusetts, New Hampshire, Vermont and Washington, D.C.

Maryland legalized gay marriage this year as well, but that state is also poised for a public vote this fall.

In Maine, voters will decide on an initiative to approve same-sex marriage three years after a referendum overturned a law passed by the Maine Legislature.

And in Minnesota, voters will decide on a constitutional amendment that would ban gay marriage there.