The Duke of Cambridge is on a two-day official visit to Vietnam to highlight the damaging effects of the illegal trade on wildlife.
While there, he urged the UK Government to go ahead with a total ban on the domestic ivory trade to stop fuelling the extinction of elephants.
William, speaking at an international conference on the illegal wildlife trade, said endangered animals are still being slaughtered in "horrifying numbers" and called for an acceleration in efforts to tackle the crisis.
He told the summit in Hanoi, Vietnam, that a "betting man would still bet on extinction" of elephants after a census revealed a 30% decline in the African variety over seven years.
But he called for nations to impose a ban on the "abhorrent" trade of ivory within their borders as one of the measures to ward off the decline.
While in Hanoi he also visited a primary school where the students were reading I'm A Little Rhino, one of a series of books produced to educate children about endangered animals and why they are threatened.
He later toured the old quarter of the city, visiting medicine shops and a cafe as part of his efforts to encourage the work of Vietnamese people to stop the use of items like rhino horn in traditional medicine. While its use is reported to be declining, traditional medicine is still a strong part of Vietnamese culture.
Before leaving the district, William joined traditional medicine experts, activists, journalists and NGOs in a typically Hanoian coffee shop for a discussion about social attitudes towards the use of illegal wildlife trade products and what actions the individuals are taking to help change them.
In recent years, William has campaigned with ex-footballer David Beckham and former Chinese basketball star Yao Ming to end the trade in ivory and other products.