The Trump administration has quietly decided to reverse an Obama-era rule banning Americans from importing body parts of African elephants killed for sport.

It comes after Donald Trump branded big game trophy hunting a “horror show” last year, and suggested he would not allow the move to go ahead.

In November, the US Fish and Wildlife Service (FWS) announced it would lift a ban on elephants imported from Zimbabwe and Zambia, maintaining wealthy hunters would help raise money for conservation efforts.

A public outcry at the decision prompted the US President to intervene. “Big-game trophy decision will be announced next week,” Mr Trump said on Twitter.

“But will be very hard pressed to change my mind that this horror show in any way helps conservation of Elephants (sic) or any other animal.”

But more than three months later, Ryan Zinke, the Interior Secretary, issued a letter dated 1 March announcing the importing of elephant trophies would now be approved on a "case-by-case basis”.

The letter cites a December ruling in a long-running lawsuit challenging the ban filed by Safari Club International and the lobbying arm of the National Rifle Association.

Mr Zinke recently told people privately that Mr Trump has called him several times to discuss what to do about elephant trophies. Neither the Interior Department nor FWS issued a press release over the last week to announce the decision, which was quickly condemned by environmental advocates.

Rescuers carry starving baby elephant on their shoulders to reunite it with its worried mum in India

"The Trump administration is trying to keep these crucial trophy import decisions behind closed doors, and that's totally unacceptable," said Tanya Sanerib, international legal director at the Center for Biological Diversity. "Elephants aren't meant to be trophies, they're meant to roam free."

Mr Trump's two adult sons are trophy hunters. A photo of Donald Trump Jr holding a knife and the bloody severed tail of an elephant he reportedly killed in Zimbabwe in 2011 sparked outrage among animal rights activists.

Mr Zinke is an avid hunter, who after arriving at the Interior Department last year ordered the arcade game "Big Buck Hunter Pro" to be installed in the employee cafeteria at the agency's Washington headquarters, a move he said would promote wildlife and habitat conservation.

In June, the department removed longstanding protections for grizzly bears near Yellowstone National Park, a step that potentially allows them to be hunted. The Fish and Wildlife Service also quietly began issuing permits in October allowing African lions killed in Zimbabwe and Zambia to be imported. Previously, only wild lions killed in South Africa were eligible.

India elephants with knitted jumpers Show all 9 1 /9 India elephants with knitted jumpers India elephants with knitted jumpers Badly treated rescued elephants at the Wildlife SOS sanctuary outside Agra, India with their newly knitted jumpers are on show for the first time, they are all effected by the cold after their ordeal at the hands of owners Roger Allen India elephants with knitted jumpers Elephant jumpers. Badly treated rescued elephants at the Wildlife SOS sanctuary outside Agra India with their newly knitted jumpers are on show for the first time, they are all effected by the cold after their ordeal at the hands of owners. Phoolkali and Laxmi (left) watch while the final touches are completed. Roger Allen India elephants with knitted jumpers Elephant jumpers. Badly treated rescued elephants at the Wildlife SOS sanctuary outside Agra India with their newly knitted jumpers are on show for the first time, they are all effected by the cold after their ordeal at the hands of owners. Phoolkali and Laxmi (left) watch while the final touches are completed. Roger Allen India elephants with knitted jumpers Elephant jumpers. Badly treated rescued elephants at the Wildlife SOS sanctuary outside Agra India with their newly knitted jumpers are on show for the first time, they are all effected by the cold after their ordeal at the hands of owners. Phoolkali and Laxmi (rear) show off their jumpers. Roger Allen India elephants with knitted jumpers Elephant jumpers. Badly treated rescued elephants at the Wildlife SOS sanctuary outside Agra India with their newly knitted jumpers are on show for the first time, they are all effected by the cold after their ordeal at the hands of owners. Phoolkali Roger Allen India elephants with knitted jumpers Elephant jumpers. Badly treated rescued elephants at the Wildlife SOS sanctuary outside Agra India with their newly knitted jumpers are on show for the first time, they are all effected by the cold after their ordeal at the hands of owners. Phoolkali and Laxmi (rear) show off their jumpers. Roger Allen India elephants with knitted jumpers Elephant jumpers. Badly treated rescued elephants at the Wildlife SOS sanctuary outside Agra India with their newly knitted jumpers are on show for the first time, they are all effected by the cold after their ordeal at the hands of owners. Suzy, (front) Phoolkali and Laxmi (rear) show off their jumpers. Roger Allen India elephants with knitted jumpers Elephant jumpers. Badly treated rescued elephants at the Wildlife SOS sanctuary outside Agra India with their newly knitted jumpers are on show for the first time, they are all effected by the cold after their ordeal at the hands of owners. Suzy, (front) Phoolkali and Laxmi (rear) show off their jumpers. Roger Allen India elephants with knitted jumpers Elephant jumpers. Badly treated rescued elephants at the Wildlife SOS sanctuary outside Agra India with their newly knitted jumpers are on show for the first time, they are all effected by the cold after their ordeal at the hands of owners. Suzy, (front) Phoolkali and Laxmi (rear) show off their jumpers. Roger Allen

The world's largest land mammal, the African elephant has been classified as threatened under the US Endangered Species Act since 1979. A licensed two-week African elephant hunt can cost more than $50,000 per person, not including airfare, according to advertised rates.

Illicit demand for elephant ivory has led to devastating losses from illegal poaching as the natural habitat available for the animals to roam has also dwindled by more than half. As a result, the number of African elephants has shrunk from about 5 million a century ago to about 400,000 remaining. And that number continues to decline each year.