Carmelo Anthony (R) of the U.S. goes up to score past Puerto Rico's Manuel Narvaez during the first round of the world basketball championships in Sapporo August 19, 2006.[Reuters]

But defending champion Serbia and Montenegro had a bad day, upset by African bronze medallist Nigeria.

LeBron James and Dwayne Wade contributed 15 and 13 points respectively in their Group D opening win as the United States took a sweet revenge on their upset 92-73 defeat to Puerto Rico at the Athens Olympics two years ago.

"It's a game of revenge," said Elton Brand, who had six points. "It doesn't matter we won by how many points. A win is a win."

Leading 57-51 into the second half, the United States opened the third quarter with a 14-5 run for a comfortable 71-56 lead. In the rest of the game, the Puerto Ricans could never cut their deficit under eight points.

The Americans showed their determination to play as a team and enjoyed a surprising balanced offense with Kirk Hinrich, Christopher Paul and Dwight Howard also scoring in double digits.

The United States' "Big Three" Carmelo Anthony, LeBron James and Dwayne Wade combined for 29 points in the first half, but Puerto Rico, led by Carlos Arroyo's 15 points, fought hard to stay within 48-47 late in the second quarter. Then Joe Johnson made two three-pointers in a row to spark a 9-4 run that gave the Americans a 57-51 lead at the half time.

Arroyo finished with 23 points and dished out five assists.

NBA All-star center Yao Ming scored a game-high 30 points, but his efforts turned out to be in vain as China lost to Italy 84-69.

Trailing 39-35 after the first half, China took the lead at 48-47 as Yao had 11 points in a 13-11 run opening the third quarter. However, Italy made six three-pointers in the rest of the period for a 67-56 advantage before enlarging the gap to 80-64 amid the fourth.

"I have never seen a team shoot the ball so well," said Yao."If you just spare them a half-arm distance, they can hit it."

Italy, who made eight three-pointers in the second half, went 13-for-25 from beyond the arc.

Yao admitted that the Chinese were out of steam, especially in defense, in the second half when the Italians pulled away.

"Yet it's not an excuse to make," he said. "Why could our opponents hold on?"

Yao, who was playing his first competitive match since breaking his foot in April, was rested towards the end of the game.

Gianluca Basile shot 9-for-14 from the field to lead Italy with 27 points with Matteo Soragna and Luca Garri adding 14 and 10 respectively.

In the other Group D clash, Slovenia sailed past Senegal 96-79.

Nigeria, who was making its second appearance at the quadrennial tournament, led most of the way for a 82-75 win over five-time world champion Serbia and Montenegro in the Group A match in Sendai.

In other Group A actions, Argentina outperformed France 80-70 and Lebanon beat Venezuela 82-72.

Elsewhere, European powerhouses Greece, Germany and Spain also claimed convincing victories in the opening round of the preliminaries.

Twenty four teams are competing in four groups with top four finishers from each group to reach the elimination round.