The United States will revise the State Department's travel advisory for Hong Kong to reflect "increased danger of punishment by the Chinese state security apparatus", President Donald Trump said on Friday (local time).

"We will be revising the State Department's travel advisory for Hong Kong to reflect the increased danger of surveillance and punishment by the Chinese state security apparatus," Trump said while addressing a press conference at Rose Garden of White House.

Trump called the new development a "tragedy" for the people of Hong Kong.

"The Chinese government's move against Hong Kong is the latest in a series of measures that are diminishing the city's longstanding and very proud status. This is a tragedy for the people of Hong Kong, people of China and indeed the people of the world," he said.

In a joint statement, the US, UK, Canada and Australia on Thursday expressed "deep concern" over China's decision to impose national security law in Hong Kong, saying the move would undermine the "one country, two systems" framework and is in direct conflict with its international obligations under the principles of the legally-binding.