The American Chamber of Commerce in Hong Kong has said that anything that changes the status of the territory "would have a chilling effect not only on U.S. trade and investment in Hong Kong but would send negative signals internationally about Hong Kong's trusted position in the global economy".
The legislation, S. 1838, requires annual reviews of Hong Kong's special trade status under American law - and sanctions against any officials deemed responsible for human rights abuses or undermining the city's autonomy.
The legislation requires the State Department to certify, at least annually, that Hong Kong is autonomous enough to justify favourable U.S. trading terms that have helped the territory grow as a world financial centre.
The legislation, approved by near unanimous consent in the House and Senate, would impose sanctions on China and Hong Kong officials for human rights violations that are perpetrated in the semi-autonomous territory.
China insists that the unrest in Hong Kong - a territory recovered from the United Kingdom in 1997 after a century of colonial rule - is its internal affair.
China denies interfering and says it is committed to the "one country, two systems" formula put in place at that time and has blamed foreign forces for fomenting unrest.
Hong Kong's protesters cheered the bill's passage, and plan to rally in the central financial district on Thursday evening.
It said the laws' basic intent is to undermine Hong Kong's prosperity and stability along with the "historical progress of the great rejuvenation of the Chinese nation".
China summoned U.S. Ambassador Terry Branstad, with Vice Foreign Minister Le Yucheng telling him to stop meddling in Hong Kong affairs. The territory's Beijing-backed leaders have offered few concessions and police have cracked down hard on protesters in increasingly violent confrontations. Instead, press secretary Adam Austen said: "Canada is very concerned by the situation in Hong Kong and, in particular, the recent rise in violence ..."
Meanwhile, pro-democracy opposition leader, Joshua Wong, urged the police to "retreat" from the campus and "set our trapped protesters free". Some 1,100 protesters have left or have been arrested.
He warned they'll "definitely protest" if police enter the campus.
Senior police officer Chow Yat Ming said the focus of the operation is not to arrest any holdouts but on removing hazardous items that are a threat to public safety, and to gather evidence of "malicious" damage to campus facilities.
"Trump had to sign this bill given the overwhelming support from Congress", said Nader Naeimi, head of dynamic markets at AMP Capital Investors Ltd.
The financial hub has enjoyed a rare lull in violence over the past week, with local elections on Sunday delivering a landslide victory to pro-democracy candidates.
Li and his fellow Hong Kong tycoons are under mounting pressure from Beijing to speak out against the protests, which present the most serious challenge to Communist Party rule since Tiananmen. Over the past week, most protesters have either surrendered or escaped.