President-elect Donald Trump hasn't even taken office yet, but it appears that his phone call to Taiwanese President Tsai Ing-wen earlier this month may have already been one of the most important foreign policy moves of his impending administration.

Chinese foreign ministry spokesman Geng Shuang has expressed "serious concern" about Trump's phone call and recent comments about Taiwan, describing the so-called "one China policy" — namely, refusing to challenge China's assertion that Taiwan isn't an independent nation but a rogue province still controlled by the Chinese government -- as the "political foundation" for positive American-Chinese relations, the Associated Press reported on Monday.

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"We urge the new U.S. leader and government to fully understand the seriousness of the Taiwan issue, and to continue to stick to the one China policy," Geng told the AP.

The Chinese government's concerns were prompted by Trump's most recent comments on "Fox News Sunday" with Chris Wallace.

"I fully understand the 'one China' policy, but I don't know why we have to be bound by a 'one China' policy unless we make a deal with China having to do with other things, including trade," Trump told Wallace.

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He also defended his acceptance of the Taiwanese phone call as a sign of his independence from China and refusal to show disrespect to Taiwan.

"I don't want China dictating to me and this was a call put in to me," Trump said. "It was a very nice call. Short. And why should some other nation be able to say I can't take a call? I think it actually would've been very disrespectful, to be honest with you, not taking it."

Trump's phone call was the first contact between an American president or president-elect and the Taiwanese head of state since President Jimmy Carter switched diplomatic recognition from Taiwan to China in 1979, as Newsweek reported on Sunday.

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After the initial Taiwanese phone call, the Obama administration said that senior White House officials had reassured China that America's "one China" policy is still in effect. The Obama administration did not elaborate on any of these statements in the aftermath of Trump's interview on Fox News Sunday.