Washington DC - Dozens of US lawmakers on Thursday urged Taiwan's political leadership to dramatically increase the island nation's defense spending as the threat from China rapidly grows.

President Lai Ching-Te has proposed $40 billion in extra defense spending over the next eight years, but the legislation has been blocked 10 times by Taiwan's parliament since early December.

Lai leads a government in which parliament is controlled by the opposition Kuomintang Party (KMT), which favors a closer relationship with the People's Republic of China (PRC).

On Thursday, a bipartisan letter signed by 37 Republican and Democratic members of Congress demanded that both Taipei and Washington "must do more to deter PRC aggression."

"For our part, the US must address the massive backlog in weapons deliveries to Taiwan," the lawmakers wrote. "Likewise, we need Taiwan to step up with us."

The bipartisan collection of lawmakers warned that Chinese President Xi Jinping "hopes to [reunify Taiwan] through illegal, coercive, aggressive, and deceptive actions that undermine Taiwan's will to resist."

"Xi remains willing to use military force to achieve his goal," they warned, referencing China's increasing use of live-fire military exercises in the Taiwan Strait and its incursions into the nation's airspace as attempts to intimidate Taipei.

The US has long been Taiwan's most important backer and biggest arms provider, and the democratic island would be heavily reliant on American support if it were to experience a conflict with China.

Asked about the letter, KMT spokesperson Niu Hsu-ting told the AFP that the party would "respond appropriately" but insisted that "we will absolutely not compromise on oversight of the budget."

China lashed out at Taiwan on Thursday over an interview Lai gave with the AFP, labeling him "a peace disruptor, crisis creator, and war instigator."