US House Speaker Paul Ryan says the federal government has "plenty of money" to combat the rapidly spreading mosquito-borne Zika virus.
"There is plenty of money in the pipeline right now, money that is not going to Ebola, that was already in the pipeline, that can go immediately to Zika," the Wisconsin Republican told reporters on Tuesday.
He provided no details, but said the money could be "reprogrammed" from other purposes.
Ryan's comment comes as Congress continues to debate an Obama administration request for $US1.8 billion ($A2.37 billion) in emergency funding to address the Zika outbreak, which the World Health Organization estimates could eventually affect as many as four million people in the Americas.
Republicans, who initially urged the administration to use funding set aside for the dwindling but still deadly Ebola outbreak in West Africa, continue to press the administration to agree to reprogram money already earmarked for other purposes.
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Republicans on the House Appropriations Committee estimate that the US Department of Health and Human Services and the State Department have up to $US2.7 billion in combined unobligated funding that could be tapped for Zika.
Democrats are pushing for new emergency funding for Zika, saying the use of money already appropriated could endanger other important programs.
"We've been hesitant to signing on, because we don't want to rob Peter to pay Paul," a Democratic aide said.
Zika is carried by mosquitoes, which transmit the virus to humans.
Much remains unknown about Zika, including whether the virus actually causes the rare birth defect microcephaly in babies.
Public health officials say that link is growing stronger with new evidence, but expect it will take months to draw preliminary conclusions from studies of the virus, and possibly years to prove a connection.
More than a dozen suspected cases of sexual transmission in the United States and France, and one case of suspected transmission through a blood transfusion in Brazil have raised questions about other ways that Zika may spread.
