With a historic upset brewing, Serbia's Bogdan Bogdanovic missed a three-pointer with two seconds left to hand the defending champions a grind-it-out victory and plenty to ponder about the fast-flowing international game.

Kyrie Irving's 15 points led six Americans in double figures in a contest that at first looked like a rout thanks to a swarming USA defence.

But Serbian big men Nikola Jokic -- the only team member to earn a living in the NBA -- and Miroslav Raduljica brought the underdogs back as the Serbian offence kept finding ways to penetrate.

USA guard Paul George admitted that the high-priced American talent -- who only began playing as a unit a few weeks ago -- were still adjusting to international play.

"We relied on natural talent to get us over this one," George said.

"That's why these international guys are special in our league. They really know how to move."

The USA has won the last three Olympic gold medals and 14 in total.

Now at 4-0 in group play, they were already guaranteed of a spot in the knockout phase starting next week.
                  
Close call            

But a loss would have been a stunning first in the Olympics since 2004, and first internationally in a decade.

The Serbs came even closer to an upset than medal hopefuls Australia, who two days earlier pushed the champions throughout much of a 98-88 American win.

The USA defence smothered the Serbs early, forcing eight first-quarter turnovers to jump out to an 18-point advantage.

Three straight slam-dunks, two on alley-oops by US centre DeAndre Jordan, made it 23-5 late in the first period, and it appeared NBA showtime had started. 

But American mental miscues and sloppy passes prevented them from putting the hammer down as action became disjointed.

The Serbs closed to 50-41 at halftime thanks to 14 first-half points inside by Raduljica, who finished with 18.

The 2.09-metre (6-foot-10) Jokic, who is just 21 but expected by many to emerge as a star for the Denver Nuggets, took over in the second half, repeatedly eluding his markers en route to 25 points.

USA coach Mike Krzyzewski called Jokic "spectacular."

"He played with the poise of a player much older. He had a great game," Krzyzewski said.

"We need to expect that from players. We're going to get their best shot."

The Serbs got it down to 94-91 with a minute to play.

The USA then missed three shots that could have secured the win, setting up Bogdanovic's three-point miss.

George said the USA players were "not too concerned," adding that they were still getting to know each other and such challenges were valuable learning experiences for the medal rounds.

Serbia, now 1-3, must beat 0-4 China on Sunday to stay alive for the knockout phase.

In other Group A games, Australia routed winless China 93-68, and France did the same to Venezuela, 96-56.

With an expected win over Venezuela on Sunday, the relieved Aussies look set to avoid the USA in the medal round until the final, if they get that far.

France also booked a spot in the quarterfinals but must pull off an upset of the USA on Sunday to have any hope of entering the kinder bracket.