In Texas, Occidental Petroleum is looking to capture carbon dioxide from two ethanol plants and inject the gas into its underground wells to help extract oil. This practice, known as enhanced oil recovery, would produce more fossil fuels. But the company says that emissions from that oil would be at least partly offset by the injected carbon dioxide that remained underground — creating a fuel that has a smaller climate impact than conventional oil.

The I.R.S. delay is striking because the tax credit was one of the few climate policies to attract bipartisan support.

Democratic backers said that carbon capture could prove necessary to cut climate change pollution from industrial sources like cement or steel plants that are otherwise hard to clean up. Republican supporters, along with coal and oil companies, saw carbon capture as a less disruptive way to reduce emissions than abandoning fossil fuels altogether.

And while many environmentalists recoiled from a policy that would aid oil extraction, some green groups said that oil industry support could help drive down the cost of carbon capture faster.

The tax credit is worth up to $50 for each ton of carbon dioxide captured and permanently buried underground, and up to $35 per ton if the captured gas is used for activities like enhanced oil recovery. To qualify, a power plant must capture at least 500,000 tons of carbon dioxide per year, which means the credit could be worth more than $200 million over its 12-year lifetime.

That’s a bigger tax break than most developers can use on their own. Instead, many will need to partner with banks or investors with large tax burdens — much as wind and solar developers have done with their own federal tax credits.