Vice President Joe Biden is calling on the Republican-led US Congress to allow an up-or-down vote on funding to combat the Zika virus without other provisions attached, calling the health threat posed by the pathogen a national emergency.
Congress has failed to approve any funding to fight the mosquito-borne virus since President Barack Obama asked for $US1.9 billion ($A2.5 billion) in February.
Lawmakers have been deadlocked for months over a $US1.1 billion funding bill.
Democrats have accused Republicans of attaching controversial provisions related to abortion and Obama's healthcare law that they cannot accept and have called for new legislation.
Republicans in turn have accused Democrats of blocking the bill to gain political advantage by portraying Republicans as obstructionists on Zika funding.
"Give us an up-or-down vote, straight, on Zika," Biden, a former Democratic senator from Delaware, said at an event on Capitol Hill with fellow Democrats from the Senate and House of Representatives.
Republicans and Democrats have huddled separately in closed meetings this week to see if they could reach a compromise during September's 19-day legislative work session.
US health officials have concluded that Zika infections in pregnant women can cause microcephaly, a birth defect marked by small head size that can lead to severe developmental problems in babies. There is no vaccine or treatment for Zika.
