Evan Vucci/Associated Press President-elect Donald Trump's controversial phone call with Taiwan's president on Friday was the work of Trump staffers and Taiwan specialists that had been months in the making, The Washington Post reported, citing sources familiar with the matter.

Stephen Yates, a national security official under President George W. Bush, told the Post that Taiwan was on the Trump transition team's list of foreign leaders to reach out to "very early on."

“Once the call was scheduled, I was told that there was a briefing for President-elect Trump," Yates said. "They knew that there would be reaction and potential blowback.”

Taiwanese media reported late Friday that Trump's team had arranged the call with President Tsai Ing-wen. A spokesman for Tsai, meanwhile, told Reuters over the weekend that “of course both sides agreed ahead of time before making contact.”



The Post report and the spokesman's statement appear to differ from the Trump team's explanation for the call, which Vice President-elect Mike Pence on Sunday said was "nothing more than a courtesy call."

Taiwan's President Tsai Ing-wen. Thomson Reuters

Pence told ABC on Sunday that Trump "took the call, accepted her congratulations and good wishes and it was precisely that."

"The President of Taiwan CALLED ME today to wish me congratulations on winning the Presidency," Trump tweeted on Friday. "Thank you!"

But Richard Grenell, a former State Department official who has advised the Trump transition effort, told the Post that "of course all head-of-state calls are well planned."

He downplayed the significance of what amounted to the first official contact between the US and Taiwan in more than 30 years, saying "there was no policy discussion" and affirming the team's awareness of the US' "One China" policy.

But Taiwan's presidential office issued a statement Saturday saying Trump and Tsai discussed issues affecting Asia and the future of US relations with Taiwan.

"The president is looking forward to strengthening bilateral interactions and contacts as well as setting up closer cooperative relations" with the US, the statement said.

The US suspended formal diplomatic relations with Taiwan in 1979 after establishing a One China position — which states that "there is but one China and Taiwan is part of China" — in an effort to establish diplomatic channels with Beijing.

Beijing views Taiwan as a province of China, whereas Taiwan — which has its own democratically elected government — has a more complicated view of the nations' relationship.

The White House was not made aware of the call until after it occurred, an administration official told Business Insider on Friday.

China's foreign minister said Saturday that the call was "just a small trick by Taiwan," and that he hopes the "cornerstone" of the US' relationship with China — the One China policy — "will not be interfered with or damaged."

The state-controlled newspaper China Daily was more critical of Trump's break with diplomatic tradition, writing in an editorial published Saturday that the call "exposed nothing but his and his transition team's inexperience in dealing with foreign affairs."

Trump took to Twitter on Sunday night to lash out at China, accusing the nation of manipulating its currency and blasting it for the military buildup in the South China Sea.

"Did China ask us if it was OK to devalue their currency (making it hard for our companies to compete), heavily tax our products going into their country (the U.S. doesn't tax them) or to build a massive military complex in the middle of the South China Sea?" Trump tweeted. "I don't think so!"