The US will shoulder the consequences of China's counter measures if Washington continues to "act arbitrarily" in regards to Hong Kong, the foreign ministry said in a statement in Beijing, Reuters reports.
Trump acknowledged last week that he was weighing the ramifications of signing the bill.
"I know that many people in Hong Kong are happy that the US Government has passed a new bill", said Figo Chan, a 23-year-old Hong Kong protester who was honoured with the John McCain Prize for Leadership at the Halifax International Security Forum in Canada last weekend.
Hong Kong's turmoil nears six months of increasingly violent pro-democracy protests triggered by a now-shelved bill that would have allowed extraditions to China.
Many see the USA legislation as symbolic, but the bills' provisions have the potential, if implemented, to upend relations between the United States and Hong Kong and change the territory's status to that of any other Chinese city.
Japan's Nikkei .N225 , Hong Kong's Hang Seng .HSI and Shanghai blue chips .CSI200 flitted in and out of positive territory, as momentum ebbed.
The acts amend the existing legislation, opening a way for imposing sanctions on human rights offenders in Hong Kong and stipulating that assessment of the developments in the region be carried out annually to determine the level of Hong Kong's autonomy from China, a key aspect of the United States' trade with the region.
But Beijing reacted furiously, warning it was ready to take unspecified "firm countermeasures".
Beijing and Hong Kong leader Carrie Lam have argued that a "silent majority" still supports the establishment and abhors the increased violence of radical protesters.
He also mentioned his support for Hong Kong, adding, "At the same time we want to see it go well in Hong Kong".
That has meant, for instance, that trade-war tariffs don't apply to exports from Hong Kong.
Asked if Trump's signing statement was aimed at the sanctions provisions, a senior administration official said the statement was drafted with all of the bill's provisions in mind. The legislation, the statement said, "will send wrong messages to demonstrators and not help alleviate the situation".
He mentioned had a in fact staunch relationship with Chinese President Xi Jinping, and anticipated him to be distinct that a determined end result within the Chinese-ruled metropolis of Hong Kong, where expert-democracy parties received practically 90% of 452 district council seats in Sunday's elections.
"If America does not speak out for human rights in China because of commercial interests, we lose all moral authority to speak out elsewhere", she said in a statement.
According to the State Department, 85,000 US citizens lived in Hong Kong in 2018 and more than 1,300 USA companies operate there, including almost every major US financial firm.