"Most recently, demand from Asia -- particularly China -- has fueled the trade, but we also know that the United States and Europe are contributing to it," he said.
At the same time, he said, recent initiatives taken around the world to destroy seized ivory, curb consumption of shark fin soup and protect snow leopards showed that concerted action could work.
UK Foreign Secretary William Hague said the issue was an unprecedented crisis that demanded a global response.
"But this is not just an environmental crisis," he said. "This is now a global criminal industry, ranked alongside drugs, arms and people trafficking. It drives corruption and insecurity, and undermines efforts to cut poverty and promote sustainable development, particularly in African countries."
U.S. market for ivory called second biggest
With the issue taking center stage, U.S. President Barack Obama signed off this week on a "National Strategy for Combating Wildlife Trafficking," which sets out ways to stem the illegal trade.
Its stated priorities are to strengthen enforcement, reduce demand for illegally trafficked wildlife and work more closely with international partners.
U.S. Humane Society President Wayne Pacelle welcomed the step in a blog post Wednesday, but he said the group was still working toward the prohibition of all ivory trade in the country.
The United States is the second largest ivory marketplace worldwide, after China, he said, in part because it's still legal to trade in "antique" ivory more than 100 years old and non-elephant ivory, such as mammoth ivory.
"Traffickers claim that ivory from recently poached elephants is antique, and they dye it to make it look old and forge documents to substantiate their claim. Or they traffic elephant ivory as 'mammoth ivory' or some other ivory-bearing species because those are not protected by law," he wrote.
It's almost impossible for members of the public or enforcement officers to tell the old from the new, Pacelle said, which "adds up to a robust legal and illegal trade of ivory" in the United States, particularly in Hawaii.
"It's just not worth putting elephants at risk in order to preserve a limited trade in antique ivory or ivory imported before certain dates," he said.
"People can live without it, and we know that even a modest amount of trade is likely to lead to widespread killing of elephants."