China on Thursday voiced strong opposition to the U.S. sanctions on four Chinese companies and one individual amid its efforts to crack down on painkiller addiction, stressing that the Chinese government has always upheld a zero tolerance policy towards drug problems.

"The wrong behavior of letting someone else take medicine when you're the one that is sick is unconstructive, and will only interfere in the anti-drug law enforcement cooperation between China and the U.S.," Wang Wenbin, a spokesperson of China's Foreign Ministry, said at a press briefing.

China urges the U.S. to respect facts and search for causes of its Fentanyl abuse problems within itself, rather than blaming other countries, Wang said.