As health experts brace for the possibility that Zika will invade the mainland US, politicians are squabbling over funding for domestic defense systems, including mosquito control and vaccine development.

In February, the Obama administration requested $1.8 billion in emergency funds to fight off the virus. But congressional Republicans argued that money allotted to fight Ebola in West Africa could be used instead. On Wednesday, after a two-month-long impasse, the White House announced that $510 million of the $2.7 billion earmarked to battle Ebola would be transferred to the Zika fight. The administration will repurpose an additional $79 million from other accounts, including funds for emergency medical supplies during epidemics and national vaccine stockpiles.

But even with the $589 million, health officials and the administration argue that they need more funding to fight Zika. The money would go to developing diagnostics and a vaccine, as well as to mosquito surveillance and control.

Health officials worry that as temperatures warm up this spring local bursts of Zika will pop up in mosquito populations, particularly in Texas and Florida. The sooner officials can get funding for prevention and preparation, the better, officials at the White House said. Any delays in funding may make outbreaks more likely or more devastating.

“We should not play with fire here,” said Shaun Donovan, director of the Office of Management and Budget. “We risk the disease getting out of control before Congress acts.”

At a CDC summit last week, Amy Pope, White House deputy assistant for homeland security, said Congress is being unfair. “What I think Congress is doing is asking the American people to choose which disease they want the most protection from,” she said, “and that just doesn’t make a lot of sense.”

Ebola flared in West Africa in the last two years, causing the worst outbreak in its history. More than 11,300 died from the disease and, for the first time, cases reached the US.

Zika, which began tearing through the Americas in 2015, is estimated to have sickened millions and has been linked to devastating birth defects and a paralyzing auto-immune disorder.