WASHINGTON — The Trump administration on Thursday moved to drop the threat of punishment to oil and gas companies, construction crews and other organizations that kill birds “incidentally,” arguing that businesses that accidentally kill birds ought to be able to operate without fear of prosecution.

Conservation groups said the proposed new regulation from the United States Fish and Wildlife Service, which operates under the Department of Interior, would substantially weaken the Migratory Bird Treaty Act of 1918 and put millions of birds in danger. The threat of fines and prosecution has, for decades, helped prod industries to take steps to protect birds, like affixing red lights on communication towers, they say.

But industry leaders and administration officials said they expected businesses to continue to voluntarily protect bird habitats. Removing the threat of punishment, they said, would bring regulatory certainty and eliminate legal disputes over whether the law covers birds killed unintentionally, whether from an oil spill or the blade of a wind turbine.

Aurelia Skipwith, director of the Fish and Wildlife Service, called bird conservation “an integral part” of the agency’s mission. By specifying that entities should be held liable only if they can be proven to have set out to kill birds, she said, “we are taking action today to make sure our rules and regulations are clear.”