Brazil's health regulator on Monday accused China of not being transparent in efforts to win emergency approval for its Covid-19 vaccine CoronaVac, currently in the final phase of trials in the hard-hit country.
In a statement, Anvisa warned against the "influence of issues related to geopolitics" in promoting vaccines.
"The Chinese criteria applied to grant the authorization of emergency use in China are not transparent," it said.
CoronaVac, produced by the Chinese private laboratory Sinovac in collaboration with the Butantan Institute of Sao Paulo, has been the subject of heated political debate in Brazil.
President Jair Bolsonaro has worked to discredit it, painting it as a tool of both the governor of the state of Sao Paulo, Joao Doria -- considered a potential rival in the next election -- and of the Chinese Communist state.
He has even referred to it as "Joao Doria's Chinese vaccine" in an effort to belittle it.
Beijing on Tuesday defended its development process, saying multiple countries had approved Chinese inoculations in a "practical manifestation of the safety and effectiveness of China's vaccines."
Chinese companies are developing vaccines "in strict accordance with scientific rules and regulatory requirements," foreign ministry spokesman Wang Wenbin told a regular press briefing.
Governor Doria said Monday that the Butantan Institute had changed its plans and would present the health regulator with a request for a definitive authorization of CoronaVac in Brazil, rather than one that would only allow for emergency use.
The application will be submitted on December 23, he said.
Doria said last week that he expected to start administering the vaccine on January 25 in his state of 46.2 million inhabitants, the most populous in Brazil.
The Brazilian government has said that it has guaranteed access to 300 million vaccine doses, primarily those developed by the University of Oxford in alliance with the AstraZeneca group and the Brazilian health institute Fiocruz.
It has also negotiated another 70 million doses from Pfizer.
Bolsonaro's administration presented a vaccination "plan" last week, but did not say when the roll-out would begin.
The Supreme Court has ordered the government to announce the start date before 1650 GMT Wednesday.
Brazil has been hit hard by the pandemic, which has already claimed more than 181,000 lives and infected almost seven million people.