A vicious battle is looming in the fight to stop the spread of Zika virus in the United States, and it’s not going to happen in the field, but in the halls of Congress.

Federal health agencies are trying to squeeze in additional funding to combat the Zika virus, but Republican lawmakers stand in their path, and it could lead to a showdown about how much the government should be spending to fight the outbreak, according to an NBC News report.

As many feared, the Zika virus has spread from South America up into Central America and into the Southeast United States. Although symptoms from the disease are mild, it has been connected to significant birth defects, and scientists are struggling to stop its advance.

Nevertheless, Republicans in Congress are skeptical of spending too much money to stop the disease. Lawmakers have been dragging their feet on providing funding to fight the virus, and have balked at Barack Obama’s $1.9 billion request for emergency funds back in February. And federal agencies say they’re burning through cash meant for other things because of Republicans’ slowness.

The House and Senate don’t appear anywhere near even approving an amount far below Obama’s request, with the Senate approving $1.1 billion and the House approving just $700 million, all of which would come from other programs. Republicans have accused the Republicans of trying to get a “slush fund” that other agencies could pull money from, and claim that there is still Ebola money left over.