China vowed to deal a "head-on blow" to the United States after it imposed more sanctions on mainland Chinese officials over Hong Kong and warned American companies of the hazards of doing business in the city.

Beijing's liaison office in Hong Kong slammed Washington on Saturday for its "unprovoked smearing" after it issued an advisory that warned of "clear operational, financial, legal and reputational risks" in the city, including from the national security law and potential retaliation against companies for compliance with US sanctions. It also dismissed the sanctions on seven officials from the office as "blatant provocations".

"The successive sanctions imposed on us by the US have no meaning, other than to fuel our contempt towards US politicians and to arouse our strong will to fight for our national interests," it said.

"Anyone who intervenes in Hong Kong's affairs had best believe that China's development will firmly continue, and we will deal a head-on blow to America's unscrupulous behaviour."

The fiery language was echoed in a separate statement from the Chinese foreign ministry's office in Hong Kong on Saturday. It dismissed the US business advisory as "nonsense", and defended the national security law as a measure that could "push Hong Kong from chaos to governance".

"The so-called US sanctions on Chinese officials cannot at all change the Chinese government's lawful efforts to safeguard national sovereignty, safety and development interests and determination to ensure Hong Kong's prosperity and stability," it said. "Instead, it just further shows the Chinese people and the people of the world the ugly face of US hegemony and power politics."

This follows earlier criticism from the office on Friday that the US was "extremely arrogant and unreasonable in its bullying".

US Secretary of State Antony Blinken said on Friday that the business advisory, along with sanctions against the seven officials, were a "clear message that the United States resolutely stands with Hongkongers".

He accused Beijing of breaking its promise to allow Hong Kong a high degree of autonomy and "stifling the democratic aspirations" of people in the city by disqualifying elected lawmakers, arresting people for expressing discontent against the government and forcing the closure of the Apple Daily newspaper.

Analysts say relations are expected to further deteriorate between the two sides, as Beijing digs in its heels over issues relating to its national sovereignty, including its response to Western sanctions on Xinjiang and Hong Kong.

The two sides have even descended into wrangling over a proposed visit to China by US deputy secretary of state Wendy Sherman over the level of access she is granted to higher-level decision makers.

Ahead of the US sanctions announcement, Xia Baolong, director of the Hong Kong and Macau Affairs Office, warned that politicians in the US and Europe who "brutally trampled on international law and interfered in our internal affairs" would only arouse China's anger and contempt.

"It will just sound the death knell of your agents in Hong Kong, those anti-China troublemakers in Hong Kong, and you will only be dropping a heavy rock on your own feet," he said, according to a transcript released by his office.

Xia also quoted President Xi Jinping's recent speech to mark the 100th anniversary of the ruling Communist Party, where he warned that foreign powers would "get their heads bashed" if they attempted to bully China.

Song Sio-chong, a professor at Shenzhen University's Centre for the Basic Laws of Hong Kong and Macau, said Beijing was prepared for a total "face-off" with Western countries over Hong Kong.

"Hong Kong is now one of the major issues in Sino-US relations where Beijing will not back down," Song said. "It is still in the escalation stage, we will continue to see Washington and Beijing engaging in such sanctions and counter sanctions."

Song said the US sanctions on mainland Chinese officials in Hong Kong would have "little effect", since the officials had already been screened for their potential links and exposure to the US and other Western countries before being posted to the city. But Beijing might have to do more to "win over" the hearts of Hong Kong civil servants, since some may worry about being targeted with US sanctions in the future.

In addition to the latest sanctions on the seven deputy officials in Beijing's liaison office in Hong Kong, Washington sanctioned 14 senior officials over the political crackdown in Hong Kong last August, including the liaison office's director Luo Huining, Xia Baolong and Hong Kong Chief Executive Carrie Lam Cheng Yuet-ngor. Lam has said she no longer has a bank account and has been "using cash every day" as a result.

In response, Beijing passed an anti-sanctions law in June, providing legal backing for its retaliatory measures against individuals and organisations responsible for imposing foreign sanctions.

China has also issued counter-sanctions against the US, the European Union, Britain and Canada over their sanctions on officials accused of human rights abuses in Xinjiang.

Alfred Wu, an associate professor at the Lee Kuan Yew School of Public Policy at the National University of Singapore, said Beijing would be determined to retaliate.

"Beijing will have to respond strongly as the Hong Kong issue concerns its sovereignty and the success of its 'one country, two systems' policy," he said. "As the US widens its sanction targets and warns its companies in Hong Kong about the anti-foreign sanctions law, it may become a self-fulfilling prophecy as Beijing has to punch back."

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