The United States' began the defence of their FIVB Women's Nations League title with a straight-sets win over Belgium in Ruse in Bulgaria today ©FIVB

The United States' began the defence of their International Volleyball Federation Women's Nations League title with a straight-sets win over Belgium in Ruse in Bulgaria today.

The US triumphed 25-23, 25-8, 25-22 in their Pool Two opener at Arena Ruse.

Andrea Drews was the top scorer of the game with 19 points, including five of the US’s six aces and a 61 per cent attacking efficiency.

Kaja Grobelna, with 12 points, was the only Belgian to score in double digits.

Today's other match in Pool Two saw Japan beat hosts Bulgaria 25-23, 21-25, 25-19, 25-23.

Competition also begun in Pool One at Stegu Arena in Opole in Poland, with victories for Thailand and Italy.

Thailand defeated Germany 26-24, 25-19, 25-22, while Italy overcame hosts Poland in a thrilling game that ended 25-15, 25-22, 18-25, 21-25, 17-15.

In Pool Four, held at Aleksandar Nikolić Hall in Belgrade, 2018 silver medallists Turkey beat South Korea 25-15, 28-26, 25-19 prior to hosts Serbia, the reigning world champions, defeated The Netherlands 25-15, 25-22, 25-19.

Completing today's action were the Pool Three games with hosts Brazil overcoming China 25-15, 25-21, 25-21 and the Dominican Republic claiming a 25-21, 22-25, 25-18, 28-26 win over Russia at the Nilson Nelson Gymnasium in Brasilia.

A second round of matches is scheduled for tomorrow before a third on Thursday (May 23). 

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.