Olympic champions the United States won 11 of their 12 pool matches in the Women's Volleyball Nations League ©Getty Images

Olympic champions the United States and world champions Serbia are set to meet in the knockout stage of the Women's Volleyball Nations League (VNL), following the conclusion of the third week of the pool stage.

The US, winners of the last three editions of the VNL, finished with 11 wins from 12 in the first stage of this year's competitions with four further victories.

They began with a 25-16, 25-21, 25-19 triumph over Belgium, and also beat Olympic bronze medallists and world champions Serbia in straight sets 25-17, 33-31, 25-16 in the final week.

The Americans followed it with a closer 25-22, 18-25, 27-25, 23-25, 18-16 victory over Turkey, who were already assured of their place in the knockout stages as they will host the VNL deciders in Ankara, and a 17-25, 25-13, 25-23, 25-18 win against Thailand.

They topped the rankings for the pool stage, while Serbia placed sixth with 3-1 wins against Germany, Canada and Japan.

Japan had won all eight matches going into the final week, but suffered four defeats to The Netherlands, Turkey, Serbia and Belgium at the 7 Chiefs Sportsplex in Calgary, where pool five matches were played.

They progressed to a quarter-final against Olympic silver medallists Brazil ranked fifth.

Brazil competed at the Armeets Arena in Sofia in pool six for their final four fixtures.

They clinched second place for the pool stage with a 25-20, 25-23, 18-25, 21-25, 15-11 win against China, followed by straight sets victories against South Korea and Bulgaria, and a 25-18, 26-24, 23-25, 25-23 success against Thailand.

European champions Italy were third for the pool stage, beating Poland and South Korea in four sets, and Bulgaria and Thailand in straight sets at the Armeets Arena in Sofia.

They are set to face China, whose pool six campaign included straight sets triumphs over Poland and the Dominican Republic and a 25-13, 19-25, 25-19, 26-24 victory over South Korea.

The other quarter-final features hosts Turkey against Thailand, the teams ranked seventh and eighth respectively in the pool stage.

Thailand lost three matches in pool six to the Dominican Republic, Brazil and Italy, but their 25-11, 25-22, 25-17 win against South Korea in their opener in Sofia proved decisive.

The Ankara Arena is set to host the final round of the Women's VNL from July 13 to 17.