North Korea is the biggest threat to humankind right now and China and the U.S. can stop it, the U.S. ambassador to China told CNBC.

"What's happening with (North Korea's) illegal and aggressive development of nuclear weapons and ballistic missiles ... This is the biggest threat to humankind right now," Ambassador Terry Branstad told CNBC in Beijing on Wednesday.

While U.S. Ambassador Branstad praised China for adopting United Nations Security Council motions for more sanctions to be imposed on North Korea, following yet another ballistic missile test by the nation last week, he said more could be done.

"I want to compliment the Chinese for the changes they've made in the last three months, they've supported both of the resolutions passed by the United Nations Security Council and I believe they're working hard to enforce the sanctions," he said.

"But I think there's still more that needs to be done. We need to keep on working together and we share the conviction that we need to denuclearize the Korean Peninsula, and China and America can play a key role in working with the rest of the world."