The 24 teams are divided into six pools of four each, with the top teams, by Sunday evening, punching their tickets for the Japanese capital next year, fivb.com reported.
They will be joining Japan, which as host has already secured one of the 12 available berths.
A further five teams will emerge from the continental Olympic qualifying contests in January to complete the Tokyo 2020 lineup.
Defending Olympic champion Brazil, which triumphed at home at Rio 2016 for its third Olympic gold in its history (after Barcelona 1992, Athens 2004) are on the Black Sea coast in Varna, up against host Bulgaria alongside Egypt and Puerto Rico.
Brazil is the only country to have played in every single edition of the Olympic Games since volleyball was introduced to the Games in Tokyo 1964.
Meanwhile, reigning world champion and Montreal 1976 Olympic gold medalist Poland faces some very tough opposition when it hosts the likes of France, alongside Slovenia and Tunisia in Gdansk.
Rio 2016 silver medalist Italy will also need to overcome a huge hurdle when it meets Sydney 2000 champion Serbia in Bari – and the rest of the oppositions, Australia and Cameroon, are not to be taken lightly either.
Three-time Olympic champion USA (Los Angeles 1984, Seoul 1988 and Beijing 2008) are on the road in their quest to make Tokyo 2020, traveling to Rotterdam to face host the Netherlands (the Atlanta 1996 Olympic gold medalist), Belgium and South Korea. The Americans were took the bronze last time around in Rio 2016.
Four-time Olympic champion (including as USSR) Russia, however, is at home in Saint Petersburg, but faces a tough challenge from Iran. The reigning European champion also meets Cuba and Mexico.
This is the only qualification pool in which all four participants had played in Rio 2016. Russia finished fourth after blowing a two-set lead against USA in the bronze medal match – Cuba and Mexico failed to make it out of pool play.
And finally, Argentina and Canada will fight it out in Ningbo, where they will also face host China and Finland for a spot at Tokyo 2020. Both the North and South Americans ranked fifth in Rio 2016, were knocked out in quarterfinals – Argentina by Brazil and Canada by Russia.