Bernie Ecclestone has admitted that next year's Singapore Grand Prix might not go ahead.

The night race on the streets of the city-state is one of the most popular events on the calendar, but a provisional 'asterisk' has been put alongside its date for 2018.

Ousted former F1 supremo Ecclestone told Brazil's Globo: "Malaysia decided that F1 was not a good investment anymore.

"They are happy with MotoGP because they say there are many fans, they sell thousands of tickets and they make money. But in F1 the opposite was happening and they lose money. So they're leaving F1.

"Singapore is more or less the same case. It cost them a fortune to do everything we asked, to look after the track, the lights for a night race, and they took everything very seriously for 10 years.

"But now it's time to make some money, but it will not be with F1."

This year's iteration is scheduled for September 17.