James hit a go-ahead layup driving to his left with eight seconds remaining, and South Sudan missed three shots to pull off a monumental upset on its final possession. James led the Americans with 25 points to go with six rebounds and seven assists.

“I like those ones better than the blowouts,” James said as he walked off the court. “At least we get tested. I like getting tested, baby. I like being tested. Those are the best ones.”

For the United States, the narrow win exposed several issues that could prove problematic when it opens group-stage play against Serbia on July 28. The Americans fell behind by 16 points in the first half as their starting lineup, featuring Joel Embiid at center, continued to struggle with slow starts and poor ball movement. South Sudan handily won the outside shooting battle, going 14 for 33 (42.4 percent) on three-pointers compared to the Americans’ 7-for-28 shooting (25 percent). And the Americans’ star-studded roster, led by James and Stephen Curry, committed 12 turnovers, many of them inexplicable.

“It was a good reminder that when we play against teams, it’s the biggest game of their lives,” Coach Steve Kerr said. “We have to expect everyone to play like that. We let our guard down as a team and as a staff, for sure. What we’ve learned with USA Basketball is that the gap has closed.”

Saturday’s exhibition was the fourth of five showcase games for the Americans before the Olympics. They beat Canada, Australia and Serbia in the first three, but their chemistry wasn’t always sharp as Kerr experimented with starting lineups and unorthodox rotations.

If not for a dominant third quarter, which the Americans won 37-18 to erase a 14-point halftime deficit and take a lead into the final period, James never would have had the chance to play hero. Kerr elected to start five bench players to open the third quarter, a decision that paid dividends with a 14-4 run that shifted the momentum.

Even so, the Americans, who nearly blew a 24-point second-half lead against Australia on Monday in Abu Dhabi, United Arab Emirates, flirted with pain again. They led by seven points with under two minutes to play, but South Sudan’s Marial Shayok made a three-pointer and a jumper to cut the lead to two. JT Thor, a second-round pick in the 2021 NBA draft who played for the Charlotte Hornets last season but is now a free agent, drilled a three-pointer to give South Sudan a 100-99 lead with 20 seconds left.

Kerr, who had seen Curry miss two jumpers and Anthony Davis miss a shot near the rim in the closing stretch, put the ball in James’s hands for the Americans’ final possession. He wasted no time driving to the rim for the go-ahead basket, and the U.S. team held on for dear life on the other end.

“South Sudan was amazing,” Kerr said. “I did not do a great job preparing our team. We did not focus enough on what [South Sudan was] capable of. That’s on me. That really allowed South Sudan to gain confidence early. … The ending was good for us, just to feel what it’s going to be like in Paris.”

Carlik Jones, a former NBA player who has played for Dallas, Denver and Chicago, missed a pull-up jumper, and Wenyen Gabriel, another former NBA player, couldn’t connect on two putback attempts before time expired. Jones had 15 points, 11 rebounds and 11 assists for South Sudan. Shayok added 24 points, including six three-pointers.

The U.S. men will face Germany on Monday in London to complete their exhibition schedule. After facing Serbia in its Olympic opener, the Americans get a rematch with South Sudan on July 31.