The move adds to strains between the two countries over trade.
China’s Foreign Ministry says there is “resolute opposition” to President Donald Trump’s signed legislation which encourages the U.S. to send senior officials to Taiwan to meet Taiwanese counterparts and vice versa.
The bill, which is non-binding, would have gone into effect on Saturday morning, even if Mr. Trump had not signed it.
The move adds to strains between the two countries over trade, as Mr. Trump has enacted tariffs and called for China to reduce its huge trade imbalance with the U.S.
This is even while Washington has leaned on Beijing to help resolve tensions with North Korea.
In a statement, China’s Foreign Ministry said it had lodged “stern representations” with the U.S., saying the law sent a “seriously wrong signal” to the forces of Taiwan independence.
“We urge the U.S. side to correct its mistake, stop official exchanges between U.S. and Taiwan officials and substantively raise relations.
“And, prudently and appropriately handle the Taiwan issue to avoid causing serious harm to Sino-U.S. ties and peace and stability in the Taiwan Strait region.”
China considers self-ruled and democratic Taiwan to be a wayward province ineligible for state-to-state relations.
China’s hostility towards Taiwan has risen since the election of President Tsai Ing-wen of the pro-independence Democratic Progressive Party in 2016.
It suspects Tsai wants to push for formal independence, which would cross a red line for Communist Party leaders in Beijing.
Tsai, though, has said she wants to maintain the status quo and is committed to ensuring peace.
Taiwan’s government has welcomed the new U.S. legislation, saying it looks forward to continuing to deepen its relationship with Washington.
Taiwan’s presidential office said in a statement earlier on Saturday that the U.S. was Taiwan’s most important ally and thanked the country for its steadfast support.
The U.S. does not have formal ties with Taiwan but is required by law to help it with self-defence and is the island’s primary source of weapons.
Defeated Nationalist forces fled to Taiwan in 1949 after losing the Chinese civil war to the Communists.