Beijing said it opposes Washington's use of domestic laws to impose unilateral sanctions and its long-arm jurisdiction on Chinese entities and individuals after Washington announced new sanctions against Pyongyang.
The United States said on Friday it was imposing its largest package of sanctions on the Democratic People's Republic of Korea.
According to the U.S. Treasury Department, the new sanctions target one individual, 27 entities, and 28 vessels located, registered, or flagged in the DPRK, the Chinese mainland, Singapore, Taiwan, Hong Kong, the Marshall Islands, Tanzania, Panama and Comoros.
Foreign Ministry spokesman Geng Shuang said on Saturday that China has lodged solemn representations to the U.S. and urges the country to immediately stop its mistaken actions to avoid harming bilateral cooperation.
China has always comprehensively and strictly implemented the DPRK-related resolutions of the United Nations Security Council and fulfilled its international obligations, he said.
China never allows Chinese citizens or enterprises to engage in activities in violation of the UN resolutions, he said.
If there are activities proved through investigation to violate the UN resolutions or Chinese law, China will deal with them in accordance with laws and regulations, he said.
The move taken by the U.S. came amid the recent positive momentum on the Korean Peninsula, as Pyongyang and Seoul have embarked on an apparent rapprochement with the Pyeongchang Winter Olympics during the past month.
The Trump administration has engaged in "maximum pressure" against the DPRK since assuming office in early 2017 to curb Pyongyang's nuclear and missile-development programs.
U.S. Treasury Secretary Steven Mnuchin said the country has already slapped more than 450 sanctions on the DPRK, about half of them in 2017.
Ruan Zongze, vice-president of the China Institute of International Studies, said exerting maximum pressure on the DPRK shows that the U.S. distrusts the thaw on the Korean Peninsula.
Washington never loosens its pressure on Pyongyang, but "maximum pressure" is not a good practice because it goes against with the improvement of inter-Korean relations due to the Winter Olympics, he said.
"The U.S. should try its best to create opportunities for more dialogue," he added.