Italy, Japan, Taiwan and India also announced mandatory tests, but Australia and UK said there were no new rules for travellers from China.
After three years of being closed to the world, China will let people travel more freely from 8 January.
But the country's ongoing Covid surge has sparked wariness.
China has officially reported about 5,000 cases a day this week, but analysts say the numbers are vastly undercounted - and the daily case load is closer to a million. Hospitals in major cities are overwhelmed and residents are struggling to find basic medicines, according to reports.
"The infection surge in China is on expected lines," Dr Chandrakant Lahariya, an Indian epidemiologist and health systems specialist in a recent interview. "If you have a susceptible population that is not exposed to the virus, cases will rise. Nothing has changed for the rest of the world, including India."
Wang Wenbin, China's foreign ministry spokesman, said on Wednesday that "Currently the development of China's epidemic situation is overall predictable and under control".
He said China believed all countries' Covid responses should be "science-based and proportionate", and should "not affect normal people-to-people exchange". He accused some countries and media of "hyping up" the situation and "distorting China's Covid policy adjustments".
China's decision to reopen its borders marks the end of the country's controversial zero-Covid policy, which President Xi Jinping had personally endorsed. Even as the rest of the world opened up and found ways to live with the virus, Beijing insisted on mass testing and sweeping, stringent lockdowns to bring cases down to zero.
The economy took a hit and people grew both exhausted and angry - in November, the frustration spilled onto the streets in rare protests against Mr Xi and his government.
Weeks later, Beijing began to roll back the policy.It's unclear how many Chinese people will travel abroad after 8 January given the number of flights are limited, and the fact that many citizens still need to renew their passports.
But the US has said that from 5 January all incoming passengers from China, Hong Kong and Macau would need to show a negative Covid test - either a PCR or rapid antigen test - taken 48 hours before their flight.
The measures also apply to passengers flying via a third country, and to those taking connecting flights through the US to other destinations.
The US Centers for Disease Control and Prevention said it was instating the measure "to help slow the spread of the virus as we work to identify and understand any potential new variants that may emerge".
It also accused China of failing to provide "adequate and transparent" Covid data, which it said was "critical" for monitoring infection surges "effectively" as well as decreasing the chances of new variants emerging.
It's unclear how many people will fly in and out of China given the limited number of flights
The true toll of daily cases and deaths in China is unknown as officials have stopped requiring cases to be reported, and changed classifications for Covid deaths. On Sunday, officials said they would also stop releasing daily case counts.
The European Commission said its health security committee will convene on Thursday to discuss "possible measures for a coordinated EU approach" to China's Covid surge.
But Italy, an EU member state and an epicentre of the virus in late 2019 and 2020, has already imposed mandatory Covid testing on all passengers from China.
Italy's health minister said this was "essential to ensure the surveillance and identification" of any new variants of the virus, and to "protect the Italian population".
Before his announcement, flights arriving in Milan were already testing passengers from China.
On one flight, which landed at the city's Malpensa Airport on 26 December, 52% of passengers were found to be positive for Covid, la Repubblica reported.
Other places have also announced restrictions on travellers from China:
Australia's Prime Minister Anthony Albanese said there would be no changes to travel regulations for passengers from China, but added that Australia is monitoring the situation closely both in China and around the world.
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