Defending champions the United States beat Serbia in four sets ©FIVB

Defending champions the United States beat Serbia in four sets as the International Volleyball Federation Women's Nations League resumed today.

The US fought back from losing the opener to claim a 23-25, 25-16, 25-15, 25-21 victory in the pool five clash at Zoppas Arena in Conegliano.

The win for the US saw them continue their 100 per cent start to this year's tournament.

They enjoyed straight-sets wins over Belgium and Bulgaria before defeating Japan in four sets during the opening set of matches last week.

The defeat for Serbia was their second of the competition so far after they lost to Turkey.

The Turkish side were unable to maintain their perfect start as they were beaten 25-23, 25-22, 25-14 by Japan in pool six at Başkent Volleyball Hall in Ankara.

In the other match played in the group, Germany overcame Russia 25-14, 25-21, 25-20.

South Korea and China, who are guaranteed a place in the final round as they will host the six-team event in July, recorded victories in pool seven at Macau East Asian Games Dome.

South Korea despatched Belgium 25-15, 25-17, 25-21, while China beat Thailand 25-21, 25-17, 25-9.

Malwina Smarzek starred for Poland in their 23-25, 25-21, 25-21, 25-17 win against Bulgaria in pool eight.

Smarzek scored 41 points for the second game of the tournament to inspire her side to victory at Omnisport Apeldoorn.

The next set of matches are scheduled to take place tomorrow.