America's Environmental Protection Agency (EPA) will stop testing harmful chemicals on animals by 2035, but the move has been dismissed as a "gift" to the chemical industry by a leading environmental group.
The EPA has in the past relied on animal testing to judge the risk of chemicals and pesticides pose to human health, but has gradually been implementing alternative tests.
The agency's chief, Andrew Wheeler, said the move to completely eliminate animal testing was borne out of his own "longstanding personal beliefs", adding that new technologies offered viable alternatives.
The announcement has been praised by animal rights groups, but has met with scepticism in some quarters.
Mr Wheeler, a former coal industry lobbyist, has overseen President Donald Trump's campaign to rollback several of his predecessor Barack Obama's environmental regulations. Earlier this month the agency weakened wildlife protections by revising the Endangered Species Act for the first time in the law's 45-year history.
Mr Wheeler's new testing directive, which will see requests and spending on mammal studies cut by 30 per cent by 2025 and eliminated completely by 2035, has been welcomed by the chemical industry
However the Natural Resources Defense Council, a leading environmental non-profit, warned that animal testing, was crucial to identifying chemicals harmful to people and the environment.
The group said that the alternative testing methods proposed by the EPA can be useful but may not be sufficient.
Jennifer Sass, a senior scientist for the group, said the EPA is phasing out the tools that lay the groundwork for protecting the public from dangers like formaldehyde and chlorpyrifos, a pesticide used on crops, animals and buildings.
Ms Sass called the EPA chief's plan a "gift" to the chemical industry that will result in a "rigged system that gives the green light to harmful chemicals".
Mr Wheeler said he is directing the EPA's leadership team to form a working group of agency experts to come up with a plan within six months "to ensure that the agency's regulatory, compliance and enforcement activities, including chemical and pesticide approvals and agency research, remain fully protective of human health and the environment."
Mr Wheeler suggested computer modelling and lab tests involving human cells and tissues could be used as an alternative to animal testing.
The agency will also provide $4.25 million (£3.53 million) in funding grants to five institutions - Johns Hopkins University, Vanderbilt University, Vanderbilt's Medical Center, Oregon State University and the University of California-Riverside - to further research alternatives to animal testing.