It's a verbal tightrope American presidents have had to walk for nearly 50 years, where even small slip-ups when stating official U.S. policy toward Taiwan and China can trigger geopolitical alarm bells.The way the U.S. views Taiwan under the "One China" policy recognizes the Chinese position that Taiwan is part of China, while still allowing for informal U.S. relations with the self-governing island.It is intended to be vague -- built on what's become known as strategic ambiguity. That is, the U.S. has agreed to ensure Taiwan has the resources to defend itself if China attempts to force a unilateral change, without saying how far it will go militarily to counter Beijing.As assistant U.S. defense secretary Joseph Nye said in 1995 to Chinese officials wondering how the U.S. would react to a Taiwan crisis: "We don't know, and you don't know.""The idea was, stick to the very careful language that's been crafted and don't vary," said Mike McCurry, former White House press secretary under Bill Clinton. "Because there are too many people listening and paying attention."Carefully balanced to protect Taiwan's security and sovereignty without promising too much but also not irking Beijing, the policy could again be pushed into the spotlight during President Donald Trump's visit to China this week. In the past, some U.S. officials have flubbed it, requiring swift diplomatic cleanup."It's the precision of the words," said John Kirby, who served across multiple Democratic administrations as a spokesman at the State Department and Pentagon and at President Joe Biden's White House. "They just have to be so extraordinarily precise when you're talking about Taiwan because, quite frankly, the stakes are enormously high."A look at how the Taiwan policy has tripped up presidents:Biden went too far repeatedlyHe suggested four times that the U.S. would intervene militarily if China were to invade Taiwan, forcing White House officials to clarify that he wasn't undoing decades of precedent.During an August 2021 ABC News interview, Biden talked about a U.S. commitment to respond militarily if NATO allies were attacked and added, "Same with Taiwan." The White House later said that U.S. policy toward Taiwan hadn't changed.Biden said during a CNN forum that October that the U.S. was committed to defending Taiwan should China attack, resulting in similar White House backtracking.In a May 2022 news conference in Tokyo, Biden said "yes" when asked if he was willing to use the military to defend Taiwan. "That's the commitment we made," he added, forcing Defense Secretary Lloyd Austin to reaffirm U.S. commitment to the "One China" policy.And Biden suggested similarly during a September 2022 interview with CBS' "60 Minutes," prompting more White House clarifications.Trump's first administration had flubsTrump was president-elect in 2016 when he took a call from Taiwanese President Tsai Ing-wen — likely the first president to do so since the U.S. severed diplomatic relations with the island in 1979. He later scoffed at the hubbub, posting: "Interesting how the U.S. sells Taiwan billions of dollars of military equipment but I should not accept a congratulatory call."The following year, the Trump White House issued a statement about a meeting in Germany between Xi and Trump that described Xi as president of the Republic of China, the formal name for Taiwan — not the correct People's Republic of China. The event's White House transcript was later altered to fix the mistake."There is a lot of difficulty to navigate a lot of these concepts. However, the reason why that is the case — a lot of misunderstanding and misspeaking — is because those concepts are conceptual traps set up by China," said Miles Yu, who was principal China policy adviser to Secretary of State Mike Pompeo during Trump's first administration. "You cannot explain something that's unexplainable."Yu, now a senior fellow and director of the China Center at the Hudson Institute, has advocated for more firmly stating the U.S. commitment to defending Taiwan. He said the concept of a "One China" policy or a "One China" principle, as Beijing calls its insistence that Taiwan is an inalienable part of China, was "completely of Chinese making.""No one inside the Chinese high command has ever believed there is any ambiguity as to America's resolve to defend Taiwan," Yu said.Instead, he said, the U.S. has long adhered to plans to defend Taiwan in proportion to Chinese threats, as evidenced by Washington repeatedly mobilizing forces to the Taiwan Strait over the years amid heightened tensions.Today, the Trump White House says there's been no change in policy but scoffs at the idea of verbal gymnastics required in stating it, noting that Trump has approved major arms sales to Taiwan over the years.The policy was always hard to articulateAfter the Chinese civil war ended in 1949, Washington recognized Chiang Kai-shek's Nationalists as China's leaders, even after that government fled from Beijing to Taiwan. But, under an agreement with Beijing beginning in 1979 with Jimmy Carter, the U.S. began adhering to the "One China" policy.Carter's administration spent months in secret negotiations with China to reach the agreement. Yet Carter later said that it "does nothing to prevent" a future president or Congress from "even going to war" to protect Taiwan.Bill Clinton, during a 1998 roundtable in Shanghai, said he supported the "three no's": The U.S. not supporting Taiwan independence; not supporting the "two Chinas" idea, which would be a separate China and Taiwan; and not backing Taiwan's admittance into international organizations.But the following year, Clinton said, "You know what I've done in the past," seeming to point to previous U.S. military interventions and suggesting he could do something similar involving Taiwan.During a 2001 interview with The Associated Press, George W. Bush was asked whether the U.S. might use military force to counter a Chinese attack on Taiwan and answered, "It's certainly an option." Bush later told CNN that didn't mean the U.S. was toughening its stance, saying, "I have said that I will do what it takes to help Taiwan defend itself."Five years later, during a state visit to Washington by then-Chinese President Hu Jintao, Bush's White House announcer mistakenly said the national anthem of the Republic of China would be played, instead of the People's Republic of China. The correct anthem was ultimately played.Some stayed on messageIn 1989, George H.W. Bush said during a banquet in China that while the U.S. adheres to "the bedrock principle that there is but one China, we have found ways to address Taiwan constructively without rancor."During a 2014 joint news conference in Beijing with Xi, Barack Obama said, "We encourage further progress by both sides of the Taiwan Strait towards building ties, reducing tensions and promoting stability on the basis of dignity and respect."Still, getting it right can be tricky."Anybody who has been at the State Department, the Pentagon or even the White House podium can tell you: When the issue of Taiwan came up, you went to your notes," Kirby said. "You didn't freelance it."Yet Kirby recalled that he "got cocky once and didn't," mischaracterizing the policy and causing "a little kerfuffle."Any big error usually first draws complaints from U.S. policy officials, Kirby said, who aren't shy with their displeasure: "You'll be highly encouraged to make a statement correcting it right away."