Formula 1's 2018 calendar: China and Singapore Grands Prix in doubt

The night-time Grand Prix in Singapore has become one of Formula 1's most iconic races

The Chinese and Singapore Grands Prix are in doubt for 2018 after being listed as provisional on the first release of the official calendar.

Governing body the FIA has published a 21-race schedule, featuring a French Grand Prix for the first time in a decade - at Le Castellet in Provence.

China and Singapore have not yet completed commercial deals on new contracts with the F1 Group.

The season starts in Australia on 25 March, with the British race on 8 July.

The year ends at Abu Dhabi's Yas Marina track on 25 November.

Silverstone is at the end of the first ever run of three consecutive races, two weeks after France on 24 June, with Austria on 1 July.

And Germany returns at Hockenheim for the final year of its current biennial deal, having dropped off the schedule in 2017 because of financial problems at the Nurburgring.

The calendar has been shuffled compared to this year's schedule to make room for the French event in early summer.

The Azerbaijan race, taking place this weekend, will next year be held on 29 April, the date occupied this year by Russia, which in 2018 will be on 30 September.