The United States said it would slash the number of Chinese nationals permitted to work at the US offices of major Chinese state-owned media outlets in response to what Washington said was Beijing's "long-standing intimidation and harassment of journalists".

Citing a "deepening crackdown" on all forms of independent reporting inside China, administration officials said Beijing's attacks on free speech were worse than they were 10 years ago, comparing them to those of the Soviet Union at the height of the Cold War.

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From March 13, Washington will cap the number of US-based Chinese nationals allowed to work at Xinhua News Agency, China Global Television Network, China Radio International and China Daily Distribution Corp at 100 from the current number of 160.

Beijing's UN ambassador said the move was not "appropriate". In a briefing on Tuesday afternoon, the country's Foreign Ministry said the US decision had caused a serious negative impact on the two countries' relations and that it reserved the right to take measures in response.

China last month revoked the visas of three Wall Street Journal reporters in Beijing after the newspaper declined to apologise for a column with a headline that called China the "Real Sick Man of Asia". Another reporter with the paper had to leave last year after China declined to renew his visa.

"For years, the government of the People’s Republic of China has imposed increasingly harsh surveillance, harassment, and intimidation against American and other foreign journalists operating in China," US Secretary of State Mike Pompeo said in a statement.

Monday's decision was not particularly linked to the Wall Street Journal case or to the content the Chinese outlets in question produced, senior State Department officials told reporters, speaking on condition of anonymity.

"We've been imploring the Chinese for years and years now to improve their treatment of journalists in China. So, this is not linked to any one particular incident," one official said, adding that the expulsion of the Wall Street Journal reporters was a "fairly egregious" example.

While the officials said the move was not an expulsion of Chinese nationals, they acknowledged that the people whose visas were contingent on their ability to work in the US could be forced to leave.

The four outlets were among five designated by the US as foreign embassies earlier this month.

'Weaponised' visas

Tensions between the two superpowers have escalated since President Donald Trump came to office three years ago, with disputes over issues ranging from trade to accusations of Chinese spying in the US and American support for Taiwan.

"We have some differences but we do not think it is appropriate for the United States to take steps in interfering with the work of journalists coming from China," China's UN Ambassador Zhang Jun told a news conference.

Foreign Ministry spokesman Zhao Lijian said the decision effectively meant some Chinese journalists would be expelled from the country.

Earlier on Monday, the Foreign Correspondents Club of China (FCCC) said in its annual report on working conditions for foreign media that the Chinese government had "weaponised" visas as part of a stepped-up campaign of pressure on foreign journalists.

It also found that 82 percent of reporters had experienced interference, harassment or violence, while 70 percent said they had had interviews cancelled after the authorities had intervened.

The FCCC noted that, for the second year in a row, not one correspondent said reporting conditions had improved.

"It is our hope that this action will spur Beijing to adopt a more fair and reciprocal approach to US and other foreign press in China," Pompeo said, while State Department officials said Washington was ready to take further action if Beijing retaliated.

The personnel caps would be placed on the organisations rather than individuals, so it would be up to the media outlets to decide the necessary staffing cuts, the officials said.

The US will also announce in the near future limits on the duration of stay for Chinese journalists, they added.