The shipment - a part of Washington's pledge to donate 80 million vaccines - will depart Fort Lauderdale , Florida, on an Azul Airlines flight Thursday evening, bound for Campinas, a city in southeastern Brazil about 100 km (62 miles) from Sao Paulo , the official said.
The donation comes as Brazil continues to battle the virus, which has claimed over half 1,000,000 lives, aggravating deep political divides before next year's presidential election and sparking unrest round the country.
The White House said scientific teams and legal and regulatory authorities from both countries worked together to make sure prompt delivery.
The one-shot J&J vaccine is seen as particularly helpful in ensuring effective vaccination rates in remote areas since it doesn't require a second dose.
The official said the vaccines had been cleared by the US Food and Drug Administration (FDA) and would come from the availability that the us had immediately available.
Brazil had already given regulatory approval to the J&J vaccine, providing the quickest path to getting an outsized number of doses to the country immediately, the official added.
Manufacturing of the J&J vaccines at Emergent BioSolutions Inc's Baltimore plant was halted in April by the FDA following a production error that led to many doses being ruined.
The White House official underscored that the doses being shipped to Brazil were safe and stressed they came with no strings attached for the govt of President Jair Bolsonaro.
"We are sharing these doses to not secure favors or extract concessions. Our vaccines don't accompany strings attached. We do this with the singular objective of saving lives," said the official.
