The Singapore Grand Prix has been cancelled for the second season in succession, the PA news agency understands.

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.

Official confirmation that the grand prix is off is expected next week.

It is understood that a number of venues could fill the void left by Singapore.

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 options open to Formula One, 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.”

F1 bosses remain confident of completing a record 23-round calendar despite the cancellation of the Singapore race and a number of fixtures appearing uncertain in the second half of the year.

The Mexican and Brazilian Grands Prix – on October 31 and November 7 – are 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.

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