The Senate moved closer to approving US$1.1 billion ($1.6 billion) in new funding to help fight the spread of the Zika virus, but House Republicans are balking at the proposal as they plan to move their own aid bill later this week.
The Senate on a 68 to 29 vote cleared a key procedural step that will now allow senators to later this week adopt a bipartisan spending amendment written by senators Roy Blunt, a Republican of Missouri, and Patty Murray, a Democrat of Washington, that beat out two competing proposals.
While it fell short of President Barack Obama's US$1.9 billion request, it was close enough to win the support of many Democrats. The amendment was added to legislation that would provide funding for veterans, transportation and housing programmes. That bill is expected to pass later this week.
The vote comes amid growing concern that the virus could spread rapidly as the mosquito population grows this northern summer.
Zika has been linked to birth defects and health issues across Latin America and the Caribbean, including parts of Mexico and Puerto Rico.
The question now is how quickly Senate leaders can settle their differences with House Republicans, who are reluctant to approve new funds unless they are offset with cuts elsewhere in the budget.
Later this week, the House is set to take up legislation that would provide US$622.1 million to battle Zika. The package redirects money leftover from battling the Ebola virus and other programmes run by the Department of Health and Human Services to a Zika fund.
House Appropriations Committee Chairman Hal Rogers, a Republican, said GOP leaders have not ruled out additional funding, but they want the Obama Administration to first provide an exact accounting of how it plans to use any new funds.
"Given the severity of the Zika crisis and the global health threat, we cannot afford to wait on the Administration any longer," Rogers said. "We have made our own funding determinations, using what information is available and through discussions with federal agencies, to craft a proposal to fight the spread of this damaging disease."
The White House issued a veto threat on the House bill and Democrats rejected the proposal immediately.