Mosquitoes are soon likely to spread the virus here.
When the Obama administration moved nearly $600 million from fighting Ebola to fighting Zika, Dr. Anthony Fauci of the NIH said it was a stop-gap measure, at best.
"When the President asked for $1.9 billion, we needed $1.9 billion," Fauchi said Monday.
"The money's in the pipeline. Our appropriators are going to address this issue -- if the need ever arises, our appropriators will address it in the appropriations process," House Speaker Paul Ryan told CBS News.
Rep. Tom Cole chairs an appropriations subcommittee considering the administration's request.
"We do believe the NIH, and we do believe the CDC," Cole told CBS News. "But have to use the resources that we have wisely."
Cole added he wasn't "going to put a date on it," but expected more funds to be available "before the end of the fiscal year," which is October 1.
Democrats and the White House favor an emergency request, which doesn't need to be funded at the expense of other programs.
"We need the money now," House Minority Leader Nancy Pelosi told CBS News. "The budget process takes a long time -- it will be practically nine months before we could get any other money, and there's no guarantee that you have the money at the end of the year."
Pelosi said she doesn't know if the money will be approved.
"I don't know, I honestly don't know and that is what has us very concerned," Pelosi said.
But Cole said he understands the importance of funding.
"You have our guarantee that, hey, we will work with you on this," Cole said, adding that the money will eventually be there if it's needed.
On Wednesday, the CDC confirmed Zika causes birth defects. That makes it all the more urgent to mount a full-scale assault against the virus and the mosquitoes that carry it.