Washington DC - Incidental killings of protected wildlife will no longer be considered unlawful, according to a Trump administration memorandum confirmed by AFP on Thursday, in a move condemned by critics as a fundamental weakening of endangered species protections.

Under the sweeping new directive, deaths resulting from foreseeable risks posed by activities such as commercial fishing or logging will be exempt from the landmark Endangered Species Act.

The September 14 memorandum, posted online by the nonprofit Center for Biological Diversity, redefines the longstanding definition of "take" – a term that relates to pursuing, killing, or capturing a species – so that it is confined to "affirmative conduct intentionally directed against a particular animal or animals."

"A vessel that inadvertently strikes a whale has not taken it, because the vessel's course was not set against the whale," the document says, quoting from the late Supreme Court Justice Antonin Scalia.

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The conservative justice wrote a dissent in a 1995 case that the memo invokes as its basis.

"Felling a tree is not a take of the bats roosting in it unless the tree is felled for the purpose of killing or capturing them."

The document was signed by Brian Nesvik, the director of the Fish and Wildlife Service, which falls under the Interior Department.

The department confirmed to AFP that the document was genuine.

"The memorandum accurately reflects the US Fish and Wildlife Service's guidance for implementing the Endangered Species Act following the final rule rescinding the regulatory definition of 'harm,'" the department said.

Conservation groups responded with dismay, arguing that most threats to endangered or threatened species are caused not by direct hunting, but by federally permitted activities.

"These changes upend the Endangered Species Act's balance of economic activity and needed protections, pushing species to the brink of extinction," Beth Lowell, vice president of Oceana, said in a statement.

The nonprofit said North Atlantic right whales would be one of the main species threatened by the changes. There are only around 380 of them left, and their main threats come from entanglement in fishing gear and collisions with ship traffic.