WASHINGTON, June 29 (Xinhua) -- U.S. arms sales to Taiwan and sanctions against some Chinese entities and individuals undermine the mutual confidence between China and the United States, Chinese Ambassador to the United States Cui Tiankai said here Thursday.

"And all these actions - sanctions against Chinese companies and especially arms sales to Taiwan - will certainly undermine the mutual confidence between the two sides and runs counter to the spirit of the Mar-a-Lago summit," Cui told reporters.

Stressing that China is always firmly opposed to arms sales to Taiwan, which, Cui said, violate the one-China principle as well as the three joint communiques between China and the United States.

On the Korean Peninsula nuclear issue, China is implementing UN Security Council resolutions "fully and effectively," said Cui.

"If there is any Chinese entity or individual that violates UN sanctions, we'll conduct our investigation and we'll pursue the case in the court with the Chinese law," said Cui.

"But we are against this kind of so-called long-arm jurisdiction by the U.S. side," added Cui.

The U.S. State Department confirmed on Thursday that it had formally notified the U.S. Congress of arms sales to Taiwan valued about 1.42 billion U.S. dollars.

U.S. Treasury Secretary Steven Mnuchin on Thursday also announced sanctions against a Chinese bank, a Chinese company and two Chinese individuals for allegedly helping the Democratic People's Republic of Korea.