The Singapore Grand Prix has been cancelled for the second season in succession.

The night race was due to take place on October 3, but a series of Covid-19 travel restrictions in the city state means it can no longer go ahead.

Formula One bosses remain confident they will be able to complete a record 23-round calendar despite the cancellation of the Singapore race and a number of fixtures appearing increasingly at risk in the second half of the year.

China, which had been due to take place in April, and Turkey, cancelled after it was placed on the UK Government’s red list, are both contenders to fill the void left by Singapore, while Austin is also prepared to host two races at the Circuit of the Americas.

The US Grand Prix is scheduled for October 24, with a second race likely to take place a week before.

An F1 spokesperson said: “We continue to work with all promoters during this fluid time and have plenty of options to adapt if needed.”

However, the Mexican and Brazilian Grands Prix – on October 31 and November 7 – are certainly vulnerable given that both countries are recording among the highest number of Covid-19 cases in the world.

Promoters of both events are keen for their respective races to go ahead but if either country is added to the red list, that is likely to pose a serious problem for F1 given that the majority of teams are based in England.

The Japanese Grand Prix is penned in for October 10, but Suzuka chiefs are keen to see how this summer’s Tokyo Olympics play out before they take a firm decision on their race.

The Australian Grand Prix, the sport’s traditional curtain-raiser in Melbourne, has been moved to November, but the country is demanding that F1 staff must be vaccinated before they are allowed into the country.

Confirming the cancellation of their race, Singapore GP deputy chairman, Colin Syn said: “To call off the event for a second year is an incredibly difficult decision, but a necessary one in light of the prevailing restrictions for live events in Singapore.

“We would not be able to deliver a full event experience fans have come to expect over the years, while safeguarding the health and safety of our fans, contractors, volunteers and staff.

“Ultimately, we have to be responsible, cautious and prudent, as safety is our number one concern.”