More than 40 of the chamber's Democrats Monday sent Majority Leader Mitch McConnell, a letter demanding a Senate vote on additional Zika funds.
The White House says the money is urgently needed to fight the spread of mosquitoes that transmit the virus, develop a vaccine and help other countries battle Zika.
"For more than two months, Congress has failed to respond to the administration's Zika request. But more importantly, Congress has failed to address a disease that has infected nearly 700 Americans in 40 states, Washington, DC, and 3 US territories, including more than 65 pregnant women," the letter read.
Obama has redirected more than USD 500 million in unspent funds to fight Ebola but the White House says it's only a temporary solution. Republicans are signaling that they'll provide some Zika money, but they haven't said how much or how soon.
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But it appears plain that they want to provide some Zika money before departing Washington for seven weeks for the political conventions and the traditional August recess.
Republicans are demanding greater detail about the request; the White House has responded by turning up the political heat.
"And I don't know what Republicans are going to say that they did to prepare for it."
Last week, House Appropriations Committee Democrats sought to attach Obama's Zika request to an unrelated spending bill but were denied by Republicans controlling the panel.