BEIJING, Dec. 20 (Xinhua) -- China Thursday expressed firm opposition to the United States on its signing into law of the Reciprocal Access to Tibet Act of 2018, saying it is a gross interference in China's domestic affairs and sent a seriously wrong message to "Tibetan independence" forces.

The U.S. act has seriously violated the basic norms of international relations and is gravely harmful to communication and cooperation between China and the United States, Foreign Ministry spokesperson Hua Chunying said.

Stressing that Tibet affairs are purely China's domestic affairs and allow no interference from other countries, Hua said Tibet and Tibetan areas in the other four regions are open to people from around the world.

Since 2015, visitors to Tibet and these regions from the United States alone totalled nearly 40,000, she said.

Meanwhile, taking into consideration of Tibet's special geographic and climatic conditions, the Chinese government has taken certain administrative measures in accordance with laws and regulations for foreigners to enter Tibet, which are totally necessary and justified, she said.

"The act's accusations against China disregard the facts and are full of prejudice, and completely unacceptable by the Chinese side," said Hua.

She warned that if the U.S. side take actions according to the act, it will definitely cause serious damage to bilateral relations and bilateral exchange and cooperation in key fields, and China will take strong measures to resolutely safeguard its own interests.

"China's door to the outside world will open wider and wider, so is Tibet. China welcomes more foreigners to visit, travel and do business in China's Tibetan areas," Hua said.

However, these people must act in line with China's laws and regulations, and fulfill necessary procedures, added the spokesperson.

China urges the United States to fully recognize the high sensitivity of the Tibet issue, stop using the Tibet issue to interfere in China's domestic affairs, and not to implement the act, otherwise, the U.S. side will take full responsibilities for the consequences, Hua said.