WASHINGTON, May 5 (AFP) - US President Joe Biden is expected to announce his strategy toward China soon, and calls are growing for him to make a clear public commitment to defend Taiwan militarily in the event of Chinese aggression.

China considers Taiwan, which has a population of 23 million, to be a rebel province that will one day return to the mainland's fold, by force if necessary.

The United States, which has diplomatically recognised Beijing since 1979, has maintained relations with Taipei and remains its most important military ally.

A US law requires Washington to help the island defend itself in the event of a conflict, but the United States has pursued a policy of "strategic ambiguity" for decades, refraining from clearly stating what circumstances would lead it to intervene militarily on Taiwan's behalf.

The aim is two-fold: to avoid provoking Beijing, which might see this as a pretext for adopting a more aggressive policy towards Taiwan, but also to curb any desire on the part of the Taiwanese government to formally declare independence, which would set off a powder keg.

This ambiguity has allowed the United States to maintain a certain stability in the region. But in the face of China's growing aggressiveness, some experts, such as the influential Council on Foreign Relations president Richard Haass, believe that "the time has come for the United States to introduce a policy of strategic clarity".

Biden should "(make) explicit that the United States would respond to any Chinese use of force against Taiwan," Haass said in an essay published by Foreign Relations magazine in September.

"Ambiguity signals to Beijing that there are questions over America's commitment to the region, exasperated by four years of an America-first mantra that shrunk US leadership in the world," Michele Lowe, a former US Navy officer and current fellow at the Chicago Council on Global Affairs, said recently.

"Clarity provides the opposite."

In recent months, the Chinese air force has increased incursions into Taiwan's air defence identification zone. The US military fears a surprise invasion by China, and they, too, criticise the lack of clarity from the executive branch.