Some political analysts say the national security law coming directly from Beijing and bypassing Hong Kong's legislature signals the start of a more authoritarian rule in the semi-autonomous city and a march toward mainland control.
The U.S. said Lam, the chief executive of Hong Kong, is "directly responsible for implementing Beijing's policies of suppression of freedom and democratic processes".
The sanctions will block all property or other assets that the individuals have within U.S. jurisdiction.
US-China tensions continue to escalate - only a few hours ago, the Trump administration moved to ban US transactions with the Chinese owners of the WeChat and TikTok apps. "Of course, I can also send 100 US dollars to Mr. Trump for freezing", he said in a statement on the office's website, reported AP.
Last week, authorities in Hong Kong drew new red lines on the limits of dissent in the financial center, barring a dozen activists from seeking office and arresting four others over social media posts. President Donald Trump has threatened to take action since Chinese officials imposed the sweeping law on Hong Kong in June.
"The United States stands with the people of Hong Kong and we will use our tools and authorities to target those undermining their autonomy", Treasury Secretary Steven Mnuchin had said in a statement.
Luo Huining, Head of China's Liaison Office in Hong Kong, said in a statement on Saturday, "the unscrupulous intentions of the U.S. politicians to support the anti-China chaos in Hong Kong have been revealed, and their clowning actions are really ridiculous".
Financial Secretary of the HKSAR government Paul Chan said in an online article that the so-called sanctions exposed the hegemonic and bullying mindset of the United States and stressed that there is no room for compromise in safeguarding national security.
"These legal provisions, coupled with the rule of law and an independent judiciary in Hong Kong, are clearly ignored by relevant USA officials who have chosen to make unsubstantiated and sweeping comments to serve their own interest", a government statement said. "We will not be intimidated", the spokesman said.
John Lee Ka-chiu, secretary for security in Hong Kong who has introduced a new police unit to enforce the new security law.
TikTok, a company owned by Beijing-headquartered ByteDance Ltd that has 100 million users in the USA and hundreds of millions worldwide, said it does not store US user data in China, has not given information to Beijing or censored content at the Chinese government's request.