The defending champions came out 25-21, 24-26, 25-21, 25-20 winners on the second day of action at Arena Ruse.

Japan's Yuki Ishii was the game's top scorer with 23 points but with lots of new blood in the US squad, the Americans once again demonstrated their strength in depth with Haleigh Washington bagging 20 and Madison Kingdon Rishel, Jordan Thompson and Hannah Tapp adding another 13 each.

Today's other match in Pool Two saw Belgium come from two games down against hosts Bulgaria to triumph 19-25, 15-25, 25-22, 25-16, 15-13 and successfully bounce back from their loss against the US yesterday.

Competition also continued in Pool One at Stegu Arena in Polish city Opole, where Italy beat Thailand 25-13, 25-17, 26-24 to continue their perfect start.

Later in the day, hosts Poland defeated Germany 25-21, 23-25, 25-23, 26-24 for their first win.

In Pool Four, hosts and reigning world champions Serbia extended their unbeaten run after coming from behind to overcome South Korea 15-25, 25-18, 25-17, 25-14 at Aleksandar Nikolić Hall in Belgrade.

Turkey joined them in making it two vctories from as many outings by beating The Netherlands 25-22, 25-14, 21-25, 25-15.

Completing today's action were the Pool Three games with hosts Brazil losing 22-25, 20-25, 25-22, 26-28 to the Dominican Republic and Russia defeating China 25-22, 16-25, 25-16, 25-23 at the Nilson Nelson Gymnasium in Brasilia.

A third round of matches is scheduled for tomorrow.

The pools will be rearranged again next week, with the same thing happening each week for five weeks. 

The top five teams after the end of the pool stage will qualify for the final round.

That will take place at Nanjing Olympic Sports Centre.

China automatically have a place in the final stage as hosts.