The US and Brazilian Grands Prix are unlikely to take place this year as a result of the coronavirus, according to Mercedes Formula 1 boss Toto Wolff.
The US, Mexican and Brazilian races are scheduled to run consecutively in late October and November but the countries have some of the worst virus outbreaks.
Wolff said: "Looking at those countries right now, you cannot possibly imagine we would be going there."
F1 is still hoping to hold a calendar of 15-18 races through 2020.
Wolff, who was talking to 5 live ahead of the first day of practice at the season-opening race in Austria this weekend, said he had been led to believe by F1 chairman and chief executive officer Chase Carey that the events in Austin, Texas and Sao Paulo, Brazil were under significant threat.
"Based on my conversations with Chase Carey, he doesn't want to close any doors but it doesn't look like we will be going there," Wolff said. "They are pretty diligent and they wouldn't go there if it was a risk for our people."
Wolff was asked only about the USA and Brazil, but the answer also applies to Mexico City.
Senior insiders say it is not impossible the races could take place, but that would only happen if the coronavirus situation markedly improved in those countries.
The F1 calendar currently comprises only eight races, all in Europe, and running over the next 10 weeks.
F1 is working on publishing the next phase of the calendar.
A number of options are being considered for races after the Italian Grand Prix, the final scheduled race on 6 September, following the official cancellation of the races in Singapore, Japan and Azerbaijan last month.
The most likely scenario following Monza is for races at Italy's Mugello, Portimao in Portugal, Sochi in Russia and Shanghai in China, while discussions are ongoing with Canada and Vietnam.
The Canadian Grand Prix in Montreal would have to take place in September because of the early onset of winter in Quebec.
Shanghai is one of the events being considered to run two races on consecutive weekends.
Under current plans, F1 still expects to finish the season in the Middle East in December with races in Bahrain and Abu Dhabi. Both have indicated they would be prepared to hold two events if necessary.