This photo courtesy of the FWS, shows confiscated elephant ivory being crushed at the FWS refuge near Denver, Colorado.

The United States has destroyed six tonnes of confiscated elephant ivory, in a move wildlife groups hailed as a bold message to criminal traffickers that the ivory is worthless.

The ivory stockpile was pulverised by an industrial rock crusher at a US Fish and Wildlife Service (FWS) refuge near Denver, Colorado on Thursday.

The move was “a clear message that the nation will not tolerate wildlife crime that threatens to wipe out the African elephant and a host of other species around the globe”, the FWS said in a press statement. Witnesses to the event included representatives of African nations and top conservationists from around the globe.

“Rising demand for ivory is fueling a renewed and horrific slaughter of elephants in Africa, threatening remaining populations across the continent,” said Secretary of the Interior Sally Jewell. “We encourage other nations to join us in destroying confiscated ivory stockpiles and taking other actions to combat wildlife crime.”

The Philippines, Kenya and Gabon have already destroyed their stockpiles of ivory tusks and trinkets.

The US stockpile was accumulated over the course of 25 years, and was seized during undercover investigations of organised smuggling operations or confiscated at the border.

The FWS said most of the ivory, prior to being seized, was headed for illegal sale in the United States or overseas.

Experts say that poachers killed 35,000 elephants last year, at a rate of 96 animals per day.