Security Law Would Finish Hong Kong: Trump

US President Donald Trump on Tuesday warned that Hong Kong could lose its status as a global financial centre if a proposed Chinese crackdown goes ahead, and promised a "very interesting" US response within days.

The Chinese legislation would ban secession, subversion, terrorism and foreign interference after months of massive, often-violent pro-democracy protests last year in the semi-autonomous territory. Hong Kong's chief executive, Carrie Lam, said Tuesday that essential freedoms would remain.

But it is "hard to see how Hong Kong can remain a financial hub if China takes over," White House press secretary Kayleigh McEnany told a briefing, saying this warning came directly from Trump.

"He's displeased with China's efforts," she said.

Trump himself was asked later by reporters if he was considering sanctions against China or restrictions on visas for Chinese students. He said that was a "very important question" and that he would do something "you'll find very interesting."

"It's something you're going to be hearing about over the next, before the end of the week. Very powerfully, I think," he said, without giving more detail.

Critics fear the new law could be a death blow to Hong Kong's treasured liberties, which are crucial to making it an international financial centre on a par with New York and London.

The announcement of plans for the law -- which will be written by Beijing and bypass Hong Kong's legislature -- sparked the biggest drop on the city's stock exchange in five years on Friday. (AFP)