Following the decision to delay the Australian and Chinese Grand Prix races, reports from Dutch magazine Formule1 say that three street races are also set to be postponed or cancelled.
Formula 1's flagship event at Monaco in May is one of those believed to be at risk of bring dropped for a second successive season due to coronavirus. The others are the next two races on the calendar at Azerbaijan and Canada in June.
The magazine cites 'various sources' for its reports but does not identify them. However RaceFans's Dieter Rencken contacted a Formula 1 spokesperson and received a flat denial of the story's claims.
"We have set out the details of the revised 2021 calendar and there are no other changes,"the spokesperson said. "The suggestion street races will not take place are completely wrong."
The issue with street circuits in particular is the long lead time in constructing the temporary track facilities, which has to get underway months in advance.
The costs involved mean that promoters need to be as certain as possible that the race will go ahead, something that is proving difficult with the rapidly changing coronavirus situation.
Although global vaccination programmes are underway, the emergence of more easily transmitted mutant COVID strains has forced new restrictions on travel which puts a question mark over the prospect of F1 being able to race in those countries.
But the report says that F1 bosses already have contingency plans in the event that the three races have to be dropped.
Turkey's Istanbul Park could step in to replace Monaco after making a successful short-notice return to the calendar in 2021.
Italy's Mugello circuit and Germany's Nurburgring are in line to host races in June should either Montreal or Baku be unavailable.
Imola's Emilia Romagna Grand Prix has already been reinstated to the 2021 calendar after China was forced to drop out. Australia has been rescheduled to November after initially being positioned as the season opener, which is now Bahrain on March 28.
The 23-race season still has one unconfirmed weekend, with May 2 believed to be headed to the Portimão circuit in Portugal, as this will make transport logistics simpler for the teams.
There are two further street races planned in 2021 later in the season, with F1 still expected to travel to Singapore in October before heading to Jeddah in Saudi Arabia in December.