China's Foreign Minister Wang Yi has dismissed the phone call between United States President- elect Donald Trump and Taiwanese President Tsai Ing-wen as a "petty gambit" by Taiwan.
His measured comments targeted at Taiwan were followed by a stronger response, with his ministry saying that China has lodged a protest with the "relevant side" in the US.
Foreign Ministry spokesman Geng Shuang urged the US "to uphold the "one China policy" and handle the Taiwan issue with "care and consideration" so as to prevent unnecessary disturbances in Sino-US ties.
Earlier, Mr Wang said the phone call was "a petty gambit by Taiwan".
"It can never change the 'one China' reality that has formed in international society, nor will it change the 'one China' policy maintained by the US government all these years," he said in response to media queries at a forum.
"The 'one China' principle is the cornerstone of a healthy Sino-US relationship. We do not wish this political foundation to be affected or destroyed in any way," he added.
Analysts who spoke to The Sunday Times called the phone call late last Friday night "significant" and said it could spell trouble for Sino-US ties.
"This is a very serious incident. Even though Mr Trump has not been inaugurated, but given his position as President-elect, this is a very significant signal," said Beijing- based academic Qiao Mu.
"I'm afraid the next four years will see testy relations between the two countries," he added.
Professor Shi Yinhong, an international relations expert at Renmin University, noted that Mr Wang was very restrained and careful in his remarks.
"Mr Wang did not mention the three words 'te lang pu' (Trump as pronounced in Chinese). This shows that Beijing will continue to observe and will not jump to any conclusion about Trump's China policy as yet," said Prof Shi.
"I believe Beijing is quietly worried about this," he added.
Independent think-tank Charhar Institute researcher Wang Chong said the phone call showed up Mr Trump and his team's inexperience and lack of a proper understanding of Sino-US and also cross-strait ties.
"Beijing will take this opportunity to warn the US and Mr Trump and put pressure on them," he added.
Cross-strait expert Zhu Songling said it is still early days to assess the impact on cross- strait ties.
"It remains to be seen how Mr Trump will formulate his cross- strait policy, especially when this is a phone call before he officially takes office," said Dr Zhu of Beijing Union University.
But another cross-strait expert, Dr Wang Weinan of the Shanghai Academy of Social Sciences, told The Sunday Times he thinks this will not bode well for both Sino-US ties and cross-strait relations.
"This has breached the well-established framework of US-Taiwan relations," he said.
Mr Trump is said to be the first US president or president-elect to speak to a Taiwanese leader since the US broke ties with Taiwan after establishing diplomatic relations with China in 1979.
While many had thought that a Trump presidency might mean less pressure for China in the region, and had hoped for warmer and more stable Sino-US ties, this unprecedented move has rattled the academic circle, said analysts.
"This first open message that Mr Trump has sent on his China policy is a negative one. This is a reminder to Beijing that expectations about Mr Trump's stance could be overly optimistic," said Prof Yin.