Sen. James Lankford (R-Okla.) is accusing President Obama of using money meant to fight diseases such as the Zika virus for an international climate change fund instead.

In an op-ed published in the Daily Signal, Lankford said Obama’s March payment of $500 million toward the United Nations’s Green Climate Fund came from a State Department account that should have been used for Zika.

{mosads}Lankford is using the transfer to support his contention that Obama has always had the funds needed to fight Zika, but chose instead to prioritize the climate fund, which Republicans have painted as a wasteful slush fund.

“Congress refused to allocate funding for the U.N. Climate Change Fund last year, so the president used this account designated for international infectious diseases to pay for his priority,” the senator wrote.

“While I understand that intelligent people can disagree on the human effects on the global climate, it is hard to imagine a reason why the administration would prioritize the U.N. Green Climate Fund over protecting the American people, especially pregnant women, from the Zika virus,” he said.

The op-ed comes as Congress and the Obama administration fight over what to do about Zika. Obama is asking for a $1.9 billion emergency appropriation, while the Senate has allocated $1.1 billion and House Republicans have proposed $622 million.

The account to which Lankford is referring is the Economic Support Fund, for which Congress provided $4.32 billion this year.

In December’s funding bill for fiscal 2016, Congress gave the administration the power to use the Economic Support Fund for international efforts to fight infectious diseases.

That funding bill did not specifically prevent any money from going to the Green Climate Fund, something House Republicans wanted.

Instead, it didn’t allocate any money specifically to the climate fund, which the administration said gives it authority to use money from places such as the Economic Support Fund for the climate program.

Numerous lawmakers, including Sens. John Barrasson (R-Wyo.) and Cory Gardner (R-Colo.) have challenged the payment, saying that because Congress didn’t specifically authorize it, it is improper.

The Green Climate Fund gets money from numerous developed countries and gives it to poorer nations to cope with the effects of climate change and cut greenhouse gas emissions.