The Duke of Cambridge has urged the 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.
The second-in-line to the throne 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.
The Duke said: "China has already signalled a total ban, the USA has instituted one, and other nations, including the United Kingdom, are considering it.
"We know now what previous generations did not - ivory treated as a commodity is the fuel of extinction.
"Ivory is not something to be desired and when removed from an elephant it is not beautiful. So, the question is: why are we still trading it? We need governments to send a clear signal that trading in ivory is abhorrent."
While the international trade has been banned since 1989, it is still possible to sell antique ivory in the UK as long as it was carved before 1947.
William said there is "much to be proud of" in the efforts to halt the extinction of animals such as rhinos, elephants, pangolins and lions.
"But the organised crime syndicates we are up against are much more agile than we are. We are getting cleverer, but we need to admit that they are getting much cleverer as well," he added.
"Their brutality continues to escalate with many more rangers killed since we gathered in London (at a previous summit) two years ago."
The Duke is on a two-day official visit to the Asian country to highlight the damaging effects the illegal trade in wildlife has on some of the world's most iconic animals.
In recent years the Duke has campaigned with ex-footballer David Beckham and former Chinese basketball star Yao Ming to end the trade in ivory and other products.
Yesterday, William visited a Vietnamese primary school to learn how children are being encouraged to protect endangered rhinos - with the help of a story book highlight the story of a young rhino.
Andrea Leadsom, the Environment Secretary, is also due to speak at the conference.
A Department for Environment, Food and Rural Affairs spokeswoman said: "The UK is doing more than ever before to tackle the illegal wildlife trade, including working together with key nations, such as Vietnam, to focus attention on the issue and drive change.
"We know even more needs to be done globally, which is why we are already investing £13 million in projects around the world to boost law enforcement, reduce demand and develop sustainable livelihoods for affected communities through our Illegal Wildlife Trade Challenge Fund."