The US has become the latest country to impose mandatory Covid tests on visitors from China, after it announced it would reopen its borders next week.
Tighter measures have also been brought in by Italy, Japan, Malaysia, Taiwan and India.
After almost three years of restrictions, China will let people travel more easily from 8 January.
At the same time, the country is facing a surge in Covid cases, leading to wariness among some countries.
However, Beijing said coronavirus rules should be brought in on a “scientific” basis, and accused some countries and media of “hyping up” the situation.
The UK government says it had no plans to re-introduce testing or other entry requirements for travellers.
On Monday and Tuesday, China announced it would ease its restrictions on travel to and from the country.
From 8 January, quarantine for travellers entering China will end, and passport applications for Chinese citizens will resume, authorities said.
Travel sites reported a spike in traffic following the announcements – and some countries revised their travel rules.
The US said that from 5 January all passengers travelling from China, Hong Kong and Macau would need a negative Covid test to enter the country in order to “slow the spread” of the virus.
A US department of health statement said air passengers would need to take a Covid test no more than two days before departure. It added that those who tested positive more than 10 days before the flight could provide documentation of recovery from Covid instead of a negative test result.
The measures applied to people flying via a third country and to passengers taking connecting flights through the US to other destinations, it said.
It said it would “continue to monitor the situation” and adjust its approach “as necessary”.
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.
The true toll of daily cases and deaths in China is unknown because officials have stopped releasing the data. Reports say hospitals are overwhelmed and elderly people are dying.