FILE - In this Oct. 10, 2016, file photo, Taiwan's President Tsai Ing-wen delivers a speech during National Day celebrations in front of the Presidential Building in Taipei, Taiwan. President-elect Donald Trump spoke Dec. 2, with the president of Taiwan, a self-governing island the U.S. broke diplomatic ties with in 1979. It is highly unusual, perhaps unprecedented, for a U.S. president or president-elect to speak directly with a Taiwanese leader and will be sure to anger China. Washington has pursued a so-called “one China” policy since 1979 when it shifted diplomatic recognition of China from the government in Taiwan to the communist government on the mainland. (AP Photo/Chiang Ying-ying, File)
FILE - In this Oct. 10, 2016, file photo, Taiwan's President Tsai Ing-wen delivers a speech during National Day celebrations in front of the Presidential Building in Taipei, Taiwan. President-elect Donald Trump spoke Dec. 2, with the president of Taiwan, a self-governing island the U.S. broke diplomatic ties with in 1979. It is highly unusual, perhaps unprecedented, for a U.S. president or president-elect to speak directly with a Taiwanese leader and will be sure to anger China. Washington has pursued a so-called “one China” policy since 1979 when it shifted diplomatic recognition of China from the government in Taiwan to the communist government on the mainland. (AP Photo/Chiang Ying-ying, File) Credit: Chiang Ying-ying

President-elect Donald Trump spoke on Friday with Taiwan’s president, a major departure from decades of U.S. policy in Asia and a breach of diplomatic protocol with ramifications for the incoming president’s relations with China.

The call is the first known contact between a U.S. president or president-elect with a Taiwanese leader since before the United States broke diplomatic relations with the island in 1979. China considers Taiwan a province, and news of the official outreach by Trump is likely to infuriate the regional military and economic power.

The exchange is one of a string of unorthodox conversations with foreign leaders that Trump has held since his election. It comes at a particularly tense time between China and Taiwan, which earlier this year elected a president, Tsai Ing-wen, who has refused to accept the notion of a unified China under Beijing’s rule. Her election angered Beijing to the point of cutting off all official communication with the island government.

It is not clear whether Trump intends a more formal shift in U.S. relations with Taiwan or China. On the call, Trump and Tsai congratulated each other on winning election, a statement from Trump’s transition office said.

“During the discussion, they noted the close economic, political, and security ties … between Taiwan and the United States,” a statement from Trump’s transition office said.

A spokeswoman for Taiwan in the United States said she could not immediately confirm that the conversation took place and said she was seeking guidance from Taiwan. The conversation was first reported by the Financial Times and the Taipei Times.

Trump tweeted out Friday evening, “The president of Taiwan CALLED ME today to wish me congratulations on winning the Presidency.”

The United States has pursued what it calls a “One China” policy since 1972, when then-President Richard M. Nixon visited China. In 1978, President Jimmy Carter recognized Beijing as the only government of both mainland China and Taiwan, and Washington closed its embassy in Taiwan a year later.

China guards the structures of its formal relationship with the United States very carefully — especially the founding document that established the One China policy. U.S. officials typically tiptoe around any mention of Taiwan or the Chinese goal of full reunification.

“This phone call calls into question whether or not Trump adheres to the basic foundation of the U.S.-China relationship,” said Evan Medeiros, a former top China adviser to President Obama who is now an adviser at the Eurasia Group. “This action guarantees that U.S.-China relations under Trump will get off to a very rocky start.”

Trump’s growing team of national-security and foreign-policy advisers includes several people who have been strong supporters of Taiwan in Republican administrations. They include Stephen Yates, deputy national security adviser under Vice President Richard B. Cheney, who was reported to be visiting Taiwan when the call occurred.

Trump apparently considered hotel investments in Taiwan earlier this year. The mayor of Taoyuan said last month that a representative from the Trump Organization had visited and was interested in constructing hotels in the northwestern Taiwanese city, according to China Times. Trump has said he will separate himself from his businesses before he is inaugurated.

In recent years, in the face of Taiwan’s waning economic power and decreasing international recognition as a separate entity from mainland China, Taiwanese diplomatic representatives in Washington have been trying to raise their stature. They have courted government officials and journalists with Taiwanese film screenings, expensive soirees and other cultural events around town.

For years it has looked like a losing battle. But the Trump call could constitute a major and unexpected coup for Taiwan’s new administration by showing the island’s continued relevance.

Michael Green, a senior Asia adviser to President George W. Bush, said the call will not necessarily lead to lasting bad blood with China.

“Taiwan is a very good friend, and it is good to let the world know that,” Green said, adding, “the president-elect’s phone call may have been unconventional, but it’s not completely unprecedented.”

Earlier on Friday, Trump reportedly extended an invitation for Philippine President Rodrigo Duterte to visit the United States next year. That would mark a startling turnabout for a foreign leader who famously called Obama a “son of a whore.”

Trump transition officials confirmed the Duterte call but did not say whether Trump had issued the invitation.

Perhaps not surprisingly, the mold-breaking Republican has infused the usually banal routine of congratulatory calls from foreign leaders with drama.

Most of the more than 50 calls held by Trump or Vice President-elect Mike Pence came without the knowledge or guidance of the State Department. That means no talking points about issues of particular importance — or land mines to avoid.

“We stand by to assist and facilitate and support communication that the transition team is having with foreign leaders,” State Department spokesman John Kirby said on Friday.

The calls have appeared haphazard and out of order — Russia and Ireland before close ally Britain, for example — and the conversations have a casual tone that the British press sniffed is “un-presidential.”

Some calls, as described by Trump aides or the other country, have elicited a raised eyebrow or two.

“The one thing you learn is, you’ve got to be very careful what you say because everything you say or tweet matters,” said William Danvers, a former senior official in the Obama State Department, Pentagon and CIA.

“You have a grace period when you’re president and you deserve it, but it’s mostly a domestic grace period,” Danvers said. “It’s not as if Kim Jong Un is going to say, ‘Oh you just became president, so I’ll hold off on my missile test.’ It kind of makes us look like we don’t know what we’re doing.”