Taipei: Taiwanese President Tsai Ing-wen says the self-governing island's democracy remains under direct threat from China, underscoring her calls for closer ties with the US and other allies.

Tsai took a lead in polls in recent months as a crackdown on protests in nearby Hong Kong escalated.

"Taiwan's most pressing challenge arises from China's expanding ambitions," Tsai said. "The situation in our region is ever-more complex and Taiwan's sovereignty - its free, democratic way of life - is under threat of being stripped away and undermined."

"We need to deepen and strengthen our international relations, and at present we are doing so in terms of economics and across the board with many countries," she said.