The defending champions, who had been on a 15-match unbeaten run in winning both the World and Europe Cup last year, lost 16-21 to put their chances of progression from Pool A - from which only two of the five teams will go forward - into question.

Former National Basketball Association player Robbie Hummel top-scored for the US with nine points, with Kareem Maddox weighing in with six at Museumsquare.

"We feel good," said Maddox.

"It’s game number one of pool play, so we’re just getting started.

"We’re ready to go."

The US finished the day top of the pool after following up with a 22-3 win over Turkey.

Serbia recovered their fortunes with an 18-14 win over last year’s silver medallists The Netherlands, who had beaten South Korea 22-8 in their opening match.

The latter side had won their opening match 22-12 against Turkey.

In Pool C, meanwhile, 2018 bronze medallists Slovenia gave early notice that they intend to do at least as well this year as they beat China 20-13 and Lithuania - who had previously beaten France 21-17 - by 21-20.

Qatar lost their opening match 13-21 to France, but went on to beat China 21-18.

In the women’s competition defending champions Italy lived up to their position as the won their two opening games in Pool D, beating New Zealand 17-12 and Ukraine 17-15.

Russia, the 2018 silver medallists, matched the defending champions as they earned a 22-5 win over Indonesia followed by a 13-12 victory over Ukraine.

New Zealand beat Indonesia 21-3 in their opening match.

France, bronze medallists last year, finished the day with a 100 per cent record in Pool B after beating Japan 16-14 and Andorra 22-6.

Australia joined them after a 22-9 win over Andorra and a 20-14 victory over Switzerland.

The latter side won 22-20 in their second match against Japan.