BEIJING — In a break with decades-long diplomatic tradition, President-elect Donald Trump spoke directly with the president of Taiwan, a move that drew an irritated response from China on Saturday and looked set to cast uncertainty over U.S. policy toward Asia.

It is perhaps unprecedented for a U.S. president or president-elect to speak directly with a leader of Taiwan, a self-governing island the U.S. broke diplomatic ties with in 1979. China said it lodged a stern complaint with the U.S. and reiterated its commitment to seeking “reunification” with the self-governed democratic island, which it considers a renegade province.

In initial comments apparently meant to downplay the significance of the call, Chinese Foreign Minister Wang Yi said Saturday that the contact between Taiwanese President Tsai Ing-wen and Trump was “just a small trick by Taiwan” that he believed would not change U.S. policy toward China, according to Hong Kong’s Phoenix TV.

“The one-China policy is the cornerstone of the healthy development of China-U. S. relations and we hope this political foundation will not be interfered with or damaged,” Wang was quoted as saying.

Taiwan’s official Central News Agency said Edwin Feulner, former president of the Heritage Foundation, a Washington-based conservative think tank, was a “crucial figure” in setting up communication channels between the sides, leading to the call. Feulner could not immediately be reached to comment on the report, which cited anonymous sources.

After the phone conversation, Trump tweeted that Tsai “CALLED ME.” He also groused about the reaction to the call: “Interesting how the U.S. sells Taiwan billions of dollars of military equipment but I should not accept a congratulatory call.”

The call also has drawn attention to Taiwanese media reports that the Trump Organization is interested in investing in the Taiwanese city of Taoyuan, near Taipei.

The Trump Organization has denied it has any projects planned in Taiwan.