West Virginia Senator Joe Manchin told reporters that a carbon tax is “not on the board” in negotiations over the Biden administration’s proposed infrastructure and spending plans.

“The carbon tax is not on the board at all right now,” the Democrat told reporters Tuesday morning. When asked whether he would get behind a carbon tax in the future, Manchin repeated that the tax was not being considered.

The carbon tax is a tax on energy production which would essentially be a fee levied on greenhouse gas emissions. Reuters describes how it works: “under a carbon tax, the government sets a gradually rising price for each ton of greenhouse gas that polluters emit, incentivizing industries to move to cleaner energy sources.”

Progressive Democrats have floated the carbon tax as an alternative clean energy initiative after Manchin opposed the Clean Electricity Performance Program, a $150 billion plan to transition away from greenhouse gas emissions in the energy industry.