China acted after the widespread and sometimes violent anti-government protests in the territory last year that Beijing saw as a dangerous campaign to split Hong Kong from the rest of China.
The U.S. has said that if the law is passed it will revoke some of the special privileges granted to Hong Kong after the former British colony was handed over to Chinese rule in 1997, while Britain has said it will offer passports and a path to citizenship to as many as 3 million Hong Kong residents. Beijing has denounced the moves as interference in its sovereign affairs.
On Wednesday, the Group of Seven leading economies called on China to reconsider its plans in a joint statement voicing grave concern regarding China's decision to impose a national security law on Hong Kong, adding that it would breach Beijing's international commitments as well as the territory's constitution.