US President-elect Donald Trump spoke with President Tsai Ing-wen of Taiwan, who offered her congratulations, Mr Trump's transition team said in a statement e-mailed to media.
"During the discussion, they noted the close economic, political, and security ties exists between Taiwan and the United States", the statement said. "President-elect Trump also congratulated President Tsai on becoming President of Taiwan earlier this year."
The fact that the two leaders spoke when the US has no official diplomatic relations with Taiwan - which China considers a renegade province - immediately triggered wide concern. The Washington Post reported that the call was the first known contact between a US president or president-elect and a Taiwanese leader since the United States broke diplomatic relations with the island in 1979.
"This is but a petty gambit (小动作) by Taiwan. It can never change the 'one China' reality that has formed in international society," he said in a measured response.
China's Foreign Ministry said hours later it had lodged "stern representations with relevant authorities in the US". Meanwhile, Taiwan's policy making body on China, the Mainland Affairs Council (MAC), said China should look at the call "calmly".
The US has followed a "one China" policy since 1972, when then-President Richard Nixon visited Beijing, thawing years of mutual suspicion.
In 1978, then President Jimmy Carter recognized Beijing as the only government of both mainland China and Taiwan; one year later the US closed its embassy in Taiwan.
The White House reaffirmed the 'one China' policy after the call.
"There is no change to our longstanding policy on cross-strait issues," National Security spokeswoman Emily Horne told AFP. "We remain firmly committed to our 'one China' policy based on the three Joint Communiques and the Taiwan Relations Act. Our fundamental interest is in peaceful and stable cross-strait relations."
Mr Daniel Blumenthal, Director of Asian Studies at the American Enterprise Institute, however, took exception to the barrage of critical media coverage of Mr Trump's phone conversation with Taiwan's President, tweeting ''China's communist political warfare has been so successful convinced US chatterers a call to Taiwan is "provocative". Sad!"
Trump too defended his call with the Taiwanese president in series of tweets.
President-elect Trump's phone calls with other world leaders have been described as informal and "breezy".
Soon after the Nov 8 election he reportedly told British Prime Minister Theresa May to let him know when she was next in town.
And just this week he told Pakistani Prime Minister Nawaz Sharif, according to a readout of the conversation from Pakistani authorities, that he would visit Pakistan and was "ready and willing to play any role that you want me to play to address and find solutions to the outstanding problems."
He reportedly added: "You are a terrific guy. You are doing amazing work which is visible in every way."
The Trump camp's statement on the conversation was more measured, but since the Pakistani side's readout has not been challenged it has been assumed to be accurate and has raised eyebrows given Pakistan's tensions with India, and the controversial presence in Pakistan of terrorist groups.
The fact that Al Qaeda leader Osama bin Laden was living in Pakistan for years before being found and killed by US forces in 2011, added some strain to Washington-Islamabad relations.
Mr Trump himself tweeted in 2011 "Get it straight: Pakistan is not our friend" after Osama bin Laden was killed in the US raid.
In 2012 he tweeted : "When will Pakistan apologize to us for providing safe sanctuary to Osama Bin Laden for 6 years?! Some 'ally'."
