Big guns enter knockouts

As the championship shifts to Saitama, north of Tokyo, for the final 16 this weekend, the title contenders will be wary of upsets with New Zealand's unexpected run to the final four and the stunning collapse of the U.S. in 2002 serving as warnings.

The U.S., looking to end a barren spell of six years without an Olympic or world title, cruised through their group to set up a clash with Australia.

With a lineup of NBA all-stars led by Cleveland Cavaliers' LeBron James and Miami Heat's Dwyane Wade, the Americans have played with enthusiasm and conviction but have also been guilty of lapses of concentration.

While the Americans have had their eyes on gold since arriving in Japan, Mike Krzyzewski will make it clear to his men that they cannot look past an Australian squad led by Andrew Bogut of the Milwaukee Bucks.

"I'm going to have to explain to our players it's 'one and done', this is not a seven-game NBA series," Krzyzewski told reporters. "We have to be ready for each game."

Spain enter the knockout phase playing with purpose and flair, riding the momentum of a 14-game unbeaten streak.

But like the country's under-achieving footballers, Spain's basketball team has a history of falling short at the big event having never won a world championship or Olympic title.

Led by Memphis Grizzlies all-star Pau Gasol, the Iberians face a major test when they take on defending champions Serbia & Montenegro, who after losing their opening three games have begun to show flashes of their pedigree.

Olympic champions Argentina, led by San Antonio Spurs guard Manu Ginobili, blitzed through group play a perfect 5-0, winning their opening three games by more than 30 points.

Next up for the Argentines is a New Zealand team that has suddenly found its stride following a stumbling start to the tournament.

The Tall Blacks had looked poised for an early exit after dropping their opening three contests but rallied with back-to-back wins over Japan and Panama and head to Saitama believing they can repeat their surprise performance of four years ago when they reached the last four.

European champions Greece achieved their perfect record with efficient but unspectacular play, while their next opponent China needed 36 points from Yao Ming and a buzzer-beating three-pointer from Wang Shipeng to edge Slovenia 78-77 and squeeze through.

Other second-round clashes include African champions Angola, the surprise package of the group phase, against France, and Germany, led by Dallas Maverick's NBA all-star Dirk Nowitzki, against Nigeria.

Olympic silver medallists Italy, whose only loss of the opening round was to the U.S., face Lithuania and Turkey meet Slovenia.