First reported by the BBC and confirmed by sources to Motorsport.com, authorities in Singapore have decided that it is not possible to go ahead with the race while travel limitations remain in place.

With the city state having kept tight control in restricting the spread of coronavirus thanks to strict entry rules, it was felt that opening up for thousands of people to attend the night race was not possible.

There has not yet been an official statement about the Singapore GP, but an F1 spokesperson made clear that the sport's commercial rights holder was working with promoters to ensure a full schedule could take place.

"We continue to work with all promoters during this fluid time and have plenty of options to adapt if needed," said the spokesman.

It is understood that F1 has multiple options to slot in to the vacant Singapore slot, but no decision has been taken yet.

Turkey and China, whose races in the first phase of this year were called off, are contenders, while a second race in the United States could be a possibility.

The Singapore GP had been due to take place on October 3, as part of a triple header that included the Russian GP on September 26 and Japan on October 10. Any race taking the same Singapore slot would need to fit in geographically with those two events.

However, another option could be to shuffle Japan forward a week, and then run a second race at Austin on October 17, one week before the USA GP on October 24.

F1 looks set to face ongoing challenges with the calendar over the second half of the season, with a number of countries continuing to face difficulties in dealing with the virus, as well as international travel restrictions.

Currently Brazil, Turkey, and the United Arab Emirates are on the UK travel red list, which means that British personnel, where the majority of teams are based, face hotel quarantine on their return home.

Australia has also been cautious about opening its borders to international travel, and that could remain a factor as its November 21 date approaches.

It is thought that the potential for races falling off the schedule in the second half of the year was a key factor in F1 electing to run a double header in Austria again, in a bid to try to get as many races completed as possible.