WASHINGTON (NYTIMES) – For years the deliberate “strategic ambiguity” in Washington’s China policy has left unclear how the United States would respond to a full-scale, amphibious invasion of Taiwan.

But an equally hard question – maybe harder, in the minds of many senior White House and defence officials – is how to respond to a slow squeeze of the island, in which Chinese forces cut off much of the access to it, physically or digitally.

That question may soon be tested for the first time in a quarter of a century. China’s declaration during House Speaker Nancy Pelosi’s visit that it would begin live-fire military exercises in six locations encircling the island could set up the largest crisis in the Taiwan Strait since 1996, when President Bill Clinton ordered a US aircraft carrier to an entry to the strait.

But those exercises were significantly farther from Taiwan’s shores than the series the Chinese government has warned mariners and aircraft that it plans. And it took place in a far more benign strategic environment, back when China’s entry into the global economy was supposed to modify its behaviour, and when Clinton would tell Chinese students that the spread of the internet would foster freedom and dissent. It was also when China’s military packed a fraction of the punch it now boasts, including anti-ship missiles developed to deter US warships from getting close.

Biden administration officials say that based on their assessments a full cutoff of access to Taiwan is unlikely – in large part because it would hurt China’s own economy at a time of severe economic slowdown.

On Friday (July 29), the Group of 7 industrialised nations, the core of the Western alliance, warned China not to retaliate for Pelosi’s visit, clearly an effort to suggest that China would be widely condemned for overreacting, much as Russia was for its invasion of Ukraine.

But US officials say they worry that the events of the next few days could trigger an unintended confrontation between China’s forces and Taiwan’s, especially if the Chinese military launches a missile over the island, or if an incursion into disputed airspace leads to a midair conflict. Something similar happened 20 years ago, when a Chinese military aircraft collided with an American intelligence-gathering plane.

As the military exercises began early Wednesday, White House and Pentagon officials were monitoring the situation closely, trying to figure out if China was sending forces into each of the areas near Taiwan’s coast it has declared closed. But their assessment was that China’s strategy is to intimidate and coerce, without triggering a direct conflict.

Outside experts were more concerned that the exercise could escalate.

“This is one of the scenarios that is difficult to deal with,” said Bonny Lin, who directed the Taiwan desk at the Pentagon and held other defence positions before moving to the Centre for Strategic and International Studies in Washington, where she heads the China Power Project. “If a military exercise transitions to a blockade, when does it become clear that the exercise is now a blockade? Who should be the first to respond? Taiwan’s forces? The United States? It’s not clear.” An exercise-turned-blockade is one of many scenarios that get “war-gamed” in Washington regularly, as US officials try to map out options before a crisis strikes. But nothing really replicates a real-life confrontation.

Biden, aides say, would have to try to walk the delicate line between avoiding folding to the Chinese and avoiding escalation.

It is even more complicated by the continuing debate over how to help Taiwan become a “porcupine,” or a country too well defended for China to invade. For all the talk of F-16 sales to Taiwan – its fleet is supposed to top 200 of the fighter aircraft by 2026 – there is growing worry that Taiwan is buying the wrong kind of gear to defend itself, and that it needs to learn some lessons from Ukraine.

It is hardly a new debate. Two years ago, a senior defence official, David F. Helvey, warned that as China’s ability to choke off the island rises, Taiwan itself can, “through smart investment, send a clear signal to Beijing that Taiwan’s society and its armed forces are committed to the defence of Taiwan.”

But he warned that the sums that Taiwan’s government was committing to acquiring new defensive technology were insufficient for a resilient defence.