A Chinese Foreign Ministry spokesperson said on Tuesday that the United States should cherish the goodwill of China and safeguard the hard-won positive situation of China-U.S. cooperation on drug control.

The spokesperson made the remarks after U.S. President-elect Donald Trump threatened to slap an additional 10 percent tariff on all Chinese imports.

China is one of the world's toughest countries on counter-narcotics, both in terms of policy and its implementation, the spokesperson noted.

Considering that fentanyl is an issue for the U.S., the spokesperson said that China, in the spirit of humanity, has given support to the U.S. response to this issue.

"As early as 2019, China officially scheduled all fentanyl-related substances and is the first country in the world ever to do so," the spokesperson said, adding that China has carried out extensive and in-depth counter-narcotics cooperation with the U.S., which has been highly productive.

The spokesperson said that China is ready to continue counter-narcotics cooperation with the U.S. on the basis of equality, mutual benefit and mutual respect.