Taiwan has been backed by successive governments in Washington, even after the US formally recognized the People's Republic of China in 1979. The island was the last refuge of nationalist forces in the Chinese civil war of the 1940s, and the communist government on the mainland has gradually sidelined its opponents in the international arena.

Washington continued to provide Taiwan with arms and commerce opportunities despite technically acknowledging that a single Chinese nation is represented by Beijing. Unlike previous US presidents, Biden has deviated from the principle of strategic ambiguity, under which the Americans decline to publicly state how far they would go in backing Taipei. The president has repeatedly pledged to intervene militarily in the event of China trying to take the island by force.

In an interview with TIME magazine published on Tuesday, Biden was asked how exactly the US military would act in the event of an armed conflict in Taiwan.

"It would depend on the circumstances," the president replied. "We're continuing to supply capacity… And we've been in consultation with our allies in the region."

He confirmed that he was not "ruling out using US military force" on the ground, but also considered other options, which he would not discuss publicly. He said: "You would then criticize me with good reason if I were to tell you."

Senior US military and intelligence officials have claimed that Beijing may be preparing its military to seize Taiwan, with several deadlines for such an operation floated over the years.

Biden told the news outlet that he had discussed the issue with Chinese President Xi Jinping during their bilateral meeting in San Francisco last year, vowing not to seek independence for Taiwan. At the same time, he said "nor will we, in fact, not defend Taiwan… if China unilaterally tries to change the status."

Beijing's stated policy is to seek peaceful reunification with the island, but it has warned that it would resort to military action in response to a formal declaration of independence. Chinese officials have claimed that some American politicians are encouraging Taipei to cross this red line.