Top Democratic US presidential contender Joe Biden expressed support Friday for protesters engaged in Hong Kong’s deepest political unrest in two decades, warning China that “the world is watching.”

The international finance hub was rocked this week by the worst political violence since its 1997 handover to Beijing, with the semi-autonomous island’s embattled leader facing mounting pressure to abandon a deeply unpopular plan to allow extraditions to China.

“The extraordinary bravery shown by hundreds of thousands in Hong Kong, marching for the civil liberties & autonomy promised by China is inspiring,” tweeted the former US vice president, who is the leading Democrat in the race to challenge President Donald Trump in 2020.

“And the world is watching,” Biden added. “All of us must stand in support of democratic principles and freedom.”

The veteran Democrat weighed in with his comments two days after Trump offered a cautious response to what he said were “massive” demonstrations, saying he hoped protesters could “work it out with China.”

On Wednesday, as opposition to the extradition bill grew within an unusually wide cross section of residents, tens of thousands of protesters in Hong Kong were dispersed by riot police firing tear gas and rubber bullets.

Photo: Todd R. Darling/HKFP.

The following day, a bipartisan group of lawmakers in Washington sought to reaffirm US commitment to democracy and human rights in Hong Kong, introducing a measure that would also threaten to remove the territory’s status as a US special trading partner.

Beijing on Friday denounced what it called “violent interference” by US lawmakers, who are critical of what they see as a worsening human rights environment in Hong Kong.

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