The Vietnamese Grand Prix was absent from a draft 2021 calendar published by Formula One on Tuesday that featured a record 23 rounds, with a debut in Saudi Arabia and Brazil returning despite fears for that race's future.
Vietnam was due to host a street race in Hanoi for the first time last April, but that was cancelled due to the Covid-19 pandemic.
The absence of the grand prix on next year's calendar has been attributed to local issues, although Formula One did not give a reason or mention Vietnam in a statement setting out the planned season.
The BBC reported the decision not to host the race followed the arrest in August of Hanoi People's Committee chairman Nguyen Duc Chung.
The April 25 slot was left vacant, with various circuits in the frame.
Formula One has never before had more than 21 races in a season.
The sport said it expected fans to be back at races after a 17-round 2020 season conducted either behind closed doors or with very limited attendances and mainly in Europe due to the new coronavirus.
"We are planning for 2021 events with fans that provide an experience close to normal and expect our agreements to be honoured," said chairman and outgoing chief executive Chase Carey.
"We have proven that we can safely travel and operate our races, and our promoters increasingly recognise the need to move forward and manage the virus.
"We are delighted to see Saudi Arabia become part of the schedule and are equally excited to return to the venues we hoped to race at in 2020."
The season will start with the Australian Grand Prix in Melbourne on March 21, with Bahrain following a weekend later. It will end in Abu Dhabi on December 5.
Saudi Arabia, with a November 28 night race along the Red Sea corniche in Jeddah, will become the 33rd country to host a Formula One race.
Brazil's race at Sao Paulo's Interlagos circuit on November 14 was subject to a new contract being agreed, as was Spain's round in Barcelona on May 9.
Formula One had planned to move to a new circuit in Rio but that has proved controversial for environmental reasons and work has yet to start.
The Dutch Grand Prix, at Zandvoort, returns for the first time since 1985 with a race on September 5 and immediately after the August 29 Belgian Grand Prix at Spa-Francorchamps. It forms part of a triple header with Italy on September 12.
Russia, Singapore and Japan will also form a first long-haul triple header on September 26, October 3 and October 10.
McLaren boss Zak Brown said the planned 23 races represented "extremely positive news" for the sport's teams and partners after a tough 2020.
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