NEW YORK (REUTERS) - More than a tonne of ivory confiscated from New York and Philadelphia was crushed in Times Square on Friday to show intolerance for elephant poaching and the illegal ivory trade, federal wildlife authorities said.

The event demonstrated the urgency for stopping the criminal trade, which is killing elephants faster than the animals are reproducing, imperiling their populations, the US Fish and Wildlife Service said.

The carved ivory, some of it still in the form of an elephant's tusk, was on display on a table in Times Square.

Officials held it up piece by piece, then placed it on a conveyer belt that fed into an enormous mechanical crusher, where it was pulverized it into dust.

"This is an illegal product and we feel that burning it or destroying it gets it out of commercial use and, therefore, there's less of a chance for it to find its way into the marketplace," said Wildlife Conservation Society spokesman John Calvelli.

"It makes it really clear that it will never be used again."

The ivory was confiscated from dealers and retailers in New York City and Philadelphia.

About 35,000 elephants are killed in Africa every year for their ivory, according to the US Fish and Wildlife Service, which organised the event in partnership with the Wildlife Conservation Society.

New York passed a law in August 2014 hardening the state's stance on the ivory trade by banning the sale of ivory and increasing penalties for ivory sales.

New York City is the largest port of entry for illegal wildlife goods in the United States, according to the New York Department of Environmental Conservation, and organisers said they hoped staging the ivory-crushing event in busy Times Square would extend the reach of their message.

"Today's ivory crush will serve as a stark reminder to the rest of the world that the United States will not tolerate wildlife crimes, especially against iconic and endangered animals," said Sally Jewell, secretary of the US Department of the Interior.