A circuit guide in the current style showing the layout and key stats about the Hanoi circuit that will debut in 2020. (1:50)

SAO PAULO, Brazil -- Lewis Hamilton is unsure whether the addition of the Vietnam Grand Prix is necessary in a Formula One calendar already standing at 21 races.

This week, Formula One confirmed that the city of Hanoi will host Vietnam's first grand prix in 2020. Although the size of that year's calendar is currently unconfirmed, F1 hopes the season will include a street race in Miami after the planned 2019 edition was postponed. Dutch media this week also reported that a deal for a race at Zandvoort has moved closer to reality.

While Hamilton did not comment on the race itself, the newly crowned five-time world champion was quick to point out his opinion that the F1 race schedule is growing in the wrong direction.

"It already feels like we are on race 25 this year, so I don't think that's a good thing personally," he said.

Hamilton goes in search of his second Brazilian Grand Prix victory, having won once before in 2016. NELSON ALMEIDA/AFP/Getty Images

When asked if he had an ideal limit in his mind, he said: "Not really. I think 18 was probably the best back in the day.

"I'm someone who really loves racing, but the season is long. It's a lot of commitment for all of us, and a lot of time away from families, and the seasons are getting longer, and the off time is getting shorter. All I can speak is for myself.

"The turnaround is so short, you start preparing for your next season often as soon as the season is done. Getting your mind turned. That's very difficult. Then you have to find a way of switching off and recovering at the same time. It's most likely I'm not going to be here when it gets to 25, that's for sure."

F1's draft calendar for next year does not include any new races, although it is set for the latest finish to a season since 1963 -- the Abu Dhabi Grand Prix will take place in the first week of December. Teams have already raised concerns about the packed calendar this year, with the unprecedented triple-header of races midway through the year of France-Austria-Great Britain proving to be unpopular with teams due to the logistical problems it created.