China says it is “seriously concerned” after President-elect Donald Trump expressed doubts about continuing to abide by the “One China” policy.
Under the policy, the US has formal ties with China rather than the island
Mr Trump said he see no reason why this should continue without key concessions.
China urged Mr Trump to understand the sensitivity of the Taiwan issue.
Beijing’s reaction came in a statement from foreign Ministry spokesman Geng Shuang, who told reporters that the “One China” policy was the basis for relations with Washington.
The “One China” understanding has been crucial to US-China relations for decades.
The US broke formal diplomatic ties with the self-ruled island of Taiwan in 1979 and switched recognition to China, ushering in a new era of deepening ties.
But even though formal diplomatic relations were broken, the US has maintained close unofficial ties with Taiwan over the years.
The dispute comes just over a week after Mr Trump took a phone call from Taiwan’s President, sparking a diplomatic row and a formal protest from Beijing.
Mr Trump said: “I don’t know why we have to be bound by a One China policy unless we make a deal with China having to do with other things, including trade.”
Mr Trump also said China was not co-operating with the US on its handling of its currency, on North Korea, or on tensions in the South China Sea.
No US president or president-elect had spoken directly to a Taiwanese leader for decades.
Mr Trump said it was not up to Beijing to decide whether he should take a call from Taiwan’s leader.
“I don’t want China dictating to me and this was a call put into me,” Mr Trump said. “It was a very nice call. Short. And why should some other nation be able to say I can’t take a call?
“I think it actually would’ve been very disrespectful, to be honest with you, not taking it.”
In the same interview, Mr Trump said he “doesn’t believe” a CIA assessment that Russian hackers tried to sway the US presidential election in his favour.
Reaction in the normally hawkish Global Times, which is linked to the ruling Communist Party, was less nuanced than the foreign ministry.
The “One China policy cannot be traded“, it warned, and called for a strong response.
“China must resolutely battle Mr Trump, only after a few serious rebuffs then will he truly understands that China and other global powers cannot be bullied.”
He may be a businessman, it went on, “but in the field of diplomacy, he is as ignorant as a child“.
China has so far been restrained in its official responses to Mr Trump, choosing instead to stress on the importance of Sino-US ties.
Its foreign ministry had previously said it would not comment on his tweets, although it labelled the Trump-Tsai phone call a “petty trick” by Taiwan.