Twice-Olympic champions Brazil have become the first team to qualify for the women's volleyball tournament at Tokyo 2020 ©Twitter/FIVB

Twice-Olympic champions Brazil have become the first team to qualify for the women's volleyball tournament at Tokyo 2020.

They did it the hard way at the International Volleyball Federation Women's Intercontinental Tokyo 2020 Qualification Tournament, beating Dominican Republic in a five-set thriller.

The Pool D hosts raced into a 2-0 lead at the Ginásio Sabiazinho in Uberlândia, only to be pegged back by the Caribbean nation.

The Brazilian's saw it out in a nervy tie-break, booking their ticket to Tokyo 2020 with a 25-22, 25-19, 23-25, 18-25, 15-10 victory.

The other match in Pool D saw Azerbaijan sweep Cameroon 25-17, 25-14, 25-20.

Elsewhere, United States narrowly avoided an almighty upset against Bulgaria in Pool C before winning win five sets.

The US twice trailed at the CenturyLink Center in Bossier City before rallying and eventually triumphing 21-25, 25-18, 21-25, 25-20, 15-10.

US will reach Tokyo 2020 if they beat Argentina, who saw off Kazakhstan 22–25, 25–8, 25–20, 25–16.

Defeat for the Americans could allow Bulgaria in if they beat Kazakhstan, while Argentina would need to win 3-0 against the Americans and hope the winless Kazakhs stun the European side.

Defending Olympic champions China are on the cusp of returning to defend their crown after eating Germany in four sets at Beilun Gymnasium, Ningbo, in Pool B.

They won 25-22, 25-22, 21-25, 25-15 and are now set to face Turkey in a winner-takes-all clash.

Turkey won in four against the Czech Republic, 25-15, 25-22, 21-25, 25-17.

Russia and South Korea are also set for a straight showdown after winning their first two group games at DS Yantarny in Kaliningrad in Group E.

They both claimed shut-out wins - Russia defeated Canada 25-13, 25-21, 25-22, while Korea beat Mexico 25-21, 25-15, 26-24.

Reigning world champions Serbia and Pool A hosts Poland also maintained their 100 per cent records with wins at Hala Orbita in Wroclaw.

Serbia comfortably beat Puerto Rico 25-14, 25-20, 25-16 and will be favourites against the Poles after they were pushed all the way by Thailand before squeezing through 25-23, 22-25, 26-28, 25-23, 15-11.

Pool F at hosts PalaCatania will also see a winner-takes-all bout, with Italy and Netherlands facing off for a spot at the Olympics.

Italy crushed Belgium 25-17, 25-17, 25-16, while the Dutch were far too good for Kenya, winning 25-17, 25-10, 25-10.

The six pool winners join hosts Japan at Tokyo 2020, with the other five places filled by continental qualifiers held in January.