The chief executive of Sinovac Biotech, the main supplier of coronavirus vaccines to Brazil, complained last month to Brazilian diplomats in Beijing that anti-China comments in Brasilia were not helping with delayed shipments, two people with knowledge of the matter told Reuters.

Sinovac CEO Yin Weidong suggested an official retraction would make for a more "fluid" relationship between China and Brazilian President Jair Bolsonaro, the sources said.

Bolsonaro, who complained during his 2018 campaign about a string of Chinese acquisitions in Brazil, said in a speech on May 5 that the coronavirus pandemic could be "chemical warfare" waged by the fastest growing nation, without naming China.

Two weeks later, at a meeting at Sinovac headquarters to discuss vaccine supplies, Weidong said a change of attitude in Brasilia would be "convenient" for a more "fluid and positive" relations with the Chinese government, according to a diplomatic cable sent to Brasilia and seen by newspaper O Globo.

The two sources confirmed to Reuters the content of the telegram reported by O Globo on Wednesday.

The meeting came as supplies began dwindling of ingredients from China needed to fill and finish Sinovac's CoronaVac vaccine at Sao Paulo's Butantan Institute biomedical center.

Sinovac has attributed delayed shipments to production bottlenecks and bureaucratic issues with export licenses.

Brazil's Foreign Ministry did not immediately respond to a request for comment.

Bolsonaro's government has denied taking an antagonistic stance to China, which is Brazil's biggest trade partner.

Yet a slowdown in vaccine ingredients from China has hampered Brazil's national immunization program, which was already well behind many countries, contributing to the world's deadliest outbreak outside the United States.

Only 10 percent of Brazilians have been fully vaccinated.

"They spoke about the importance of a good political relationship," one source said of Weidong's meeting with the diplomats. "Criticism does not help. The chief executive gave the impression that this explained the delays."

The head of Butantan, Dimas Covas, testified in a senate commission of inquiry that Bolsonaro's remarks are to blame for delayed imports of vaccine ingredients from China.

Sinovac CEO Yin Weidong sought official retraction of Brazil's anti-China comments