China has said it would retaliate after US President Donald Trump ordered an end to preferential trade treatment for Hong Kong.

In a statement on Wednesday, China’s foreign ministry said it “firmly opposes and strongly condemns” the Hong Kong Autonomy Act, which unanimously passed the US Congress earlier this month and approves sanctions on Chinese officials and banks over Beijing’s clampdown on Hong Kong.

“China will make necessary responses to protect its legitimate interests, and impose sanctions on relevant US personnel and entities,” the ministry added, without elaborating.

President Donald Trump had on Tuesday ordered an end to Hong Kong’s special status under U.S. law to punish China for what he called “oppressive actions” against the former British colony.

“Today I signed legislation, and an executive order to hold China accountable for its aggressive actions against the people of Hong Kong,” Trump stated.

“Hong Kong will now be treated the same as mainland China – no special privileges, no special economic treatment and no export of sensitive technologies,” he said.

“Their freedom has been taken away; their rights have been taken away,” Trump added. “And with it goes Hong Kong, in my opinion, because it will no longer be able to compete with free markets. A lot of people will be leaving Hong Kong.”

Trump’s executive order on Tuesday said the US property of any person determined to be responsible for or complicit in “actions or policies that undermine democratic processes or institutions in Hong Kong” would be blocked.

It also directs officials to “revoke license exceptions for exports to Hong Kong”, and include revoking special treatment for Hong Kong passport holders.

U.S. relations with China have already been strained over the coronavirus pandemic, China’s military buildup in the South China Sea, the country’s treatment of Uighur Muslims and the massive trade surpluses.