The White House doesn't seem to know how much money it has on hand to battle the growing threat of the mosquito-transmitted Zika virus, even as it continues to demand $1.9 billion in new spending.

The Obama administration in April shifted about $590 million from a fund aimed at controlling the Ebola virus, to combat the new Zika threat. But administration officials have been unable to answer how much of that money is left.

The White House, the Centers for Disease Control and the Office of Management and Budget were all unable to provide an exact number or even an estimate, despite repeated requests. Not even House appropriators can find out exactly how much money is available and how it is to be spent, aides told the Washington Examiner.

It's a critical question, because Congress is trying to determine how much money is needed to fight Zika only until Sept. 30, when the current fiscal year ends. On Oct. 1, a new fiscal spending year begins, and Congress will likely provide additional funds for Zika for the next year through the appropriations process over the summer, congressional appropriators said.

The virus causes severe birth defects and experts warn it could become transmitted by mosquitos within the United States soon, particularly in southern coastal states.

But the lack of information from the Obama administration is a key reason the House GOP has resisted supporting emergency legislation that would provide new funding that can last the next four months. Instead, House Republicans last month passed legislation that would enable the Obama administration to shift an additional $622 million, much of it from the Ebola fund, to fight Zika.

Republicans argue the Obama administration could redirect as much as $2 billion in existing funding to combat the virus but is simply unwilling to use it. House Appropriations Committee Chairman Harold Rogers, R-Ky., called the $2 billion "a slush fund."

But Rogers has repeatedly complained that he has no information from the Obama administration, which he says has been unwilling to explain how they are spending the $590 million, and how much has been spent so far.

"Nobody knows how much the administration has spent on Zika," Dan Holler, spokesman for the conservative Heritage Action, told the Examiner. "They are requesting $1.9 billion, but they have not made clear what that would be used for, and what they've spent or how fast they are spending the $590 million."

The Senate last month passed legislation providing $1.1 billion in new funding for Zika that is not offset. It's less than Obama's request, but still too much for many House Republicans, who are insisting only existing funding is utilized.

Despite the imperfect information, House and Senate negotiators are "making progress" on a compromise, according to two top GOP Senate aides.

In the meantime, some local governments most threatened by Zika are so far taking on the virus without any federal help.

"Louisiana has not received any federal dollars to battle Zika," Robert Johannessen, an official with the state's Department of Health and Hospitals," told the Examiner.

The Democratic governor of Louisiana, John Bel Edwards, sent a letter this week to the state's U.S. congressional delegation, urging them to help pass a bill that provides the new federal money. The cash is needed, Edwards said, for "enhanced surveillance, testing and mosquito control activity."

But Johannessen of Louisiana's health department undercut that message by saying the money isn't needed yet. He said state funding on hand is "sufficient to support the preparation for Zika," but said more money would be needed "if we had to battle the virus if local transmission was established."