WASHINGTON  A letter from two senators is the only thing blocking congressional approval of a decade-long effort to build a women's history museum in the nation's capital.

Sens. Tom Coburn, R-Okla., and Jim DeMint, R-S.C., have placed a "hold" on a bill that would sell land near the Smithsonian Institution for the National Women's History Museum. A "hold" is a Senate practice that prevents bills from passing with unanimous consent — and implicitly threatening a filibuster.

The senators say their concerns are financial: Though the museum would pay fair market value for the land, the group has raised little money. And they said the new institution would duplicate more than 100 similar museums — some of which already get taxpayer subsidies.

Abortion politics are also in play: The senators' action came two days after the Concerned Women for America, a conservative group, wrote DeMint asking for a hold. The group's CEO, Penny Nance, wrote in July that the museum would "focus on abortion rights without featuring any of the many contributions of the pro-life movement in America."

The House passed the bill last year. Unless the Senate takes it up soon, supporters will have to start over with a new Congress next year.

"What they are doing is holding us to a standard that no museum associated with men has ever been held to," museum CEO Joan Wages said. "The content of the museum is being questioned, and it hasn't even been built. The Holocaust museum, the African-American history museum, the Native American museum — they all had very little money in the bank when Congress passed their legislation."

The museum got a push last week from actress Meryl Streep, who headlined a $350-a-plate gala in Washington. Streep herself pledged $1 million — as did former Abbott Laboratories CEO Duane Burnham. "We will get permission, because I can't imagine those two senators who have put a hold on our museum have the stomach for war with the women of America," Streep said.

In their hold letter to Minority Leader Mitch McConnell, the GOP senators said the museum was "a laudable undertaking." But while the museum isn't asking for a subsidy now, Coburn and DeMint said "taxpayers simply cannot be guaranteed of this in the future."

The site is a block south of the National Mall. An estimate by Congressional Budget Office analyst Matthew Pickford said the land is probably worth less than $60 million. The bill's sponsor, Sen. Susan Collins, R-Maine, told USA TODAY she's negotiating with DeMint and hopes to work out a deal. She said opponents had "misconceptions about what the museum would entail."

DeMint spokesman Wesley Denton said in a statement that DeMint met with museum officials. "While there are still concerns with potential taxpayer exposure and bias, we look forward to working with the proponents to see if these concerns can be addressed."

The Concerned Women for America notes that most of the museum's board has a history of abortion rights.

Wages said the topic has never come up. "We are not going to do an exhibit on that issue because we have to raise $400 million. We cannot afford, literally, to focus on issues that are divisive," she said. "The reasons for the hold just don't hold water. It should not be held up because two male senators want to stop women from knowing their history."