In an unexpected challenge for the defending Olympic gold medalists, Team USA held on to narrowly defeat South Sudan 101-100 at the USA Basketball Showcase in London's O2 Arena. Team USA fended off a strong-looking South Sudan through a game of bad shooting to earn its fourth win of the pre-Olympic friendly series.

After a sluggish first half that ended with the U.S. down by 14 points at halftime, a USA comeback in the third quarter sent the game down to the wire. In a dramatic finish, LeBron James drove for the game-winning layup with eight seconds remaining to give Team USA the well-fought win.

Saturday marked the team's first game since moving from its training ground in Abu Dhabi to Europe, and was the team's fourth pre-Olympic tuneup, with the team beating Canada and Serbia but nearly losing to Australia. However, Team USA, which is hoping to earn a fifth straight Olympic gold medal in Paris, looked especially rattled on Saturday against an unexpectedly wily South Sudan, before eventually pulling out the win.

It was a rough first half for Team USA, with the Americans taking an early lead that quickly dissipated. South Sudan took the lead with three minutes left in the first quarter, and didn't look back for the rest of the half. While the U.S. struggled to score, South Sudan looked strong from beyond the arc, pulling even further away in the second quarter.

After being up by as many as 16 points in the first half, South Sudan headed to the locker room with a 58-44 lead over the U.S.

Team USA was plagued by turnovers and missed shots throughout, going 1 for 12 on 3-pointers in the first half despite getting a number of strong looks. Meanwhile on the other end of the court, South Sudan played efficiently, playing with confidence while sinking 3s and keeping the pace fast.

Team USA looked better coming out of the locker room — no doubt on the heels of a stern talking-to from head coach Steve Kerr — and started to chip away at South Sudan's lead in the third quarter. As the Team USA's scoring slowed again, a Jrue Holiday save-turned-James dunk shifted the momentum back to the U.S.

With more of their shots landing and with a stronger defensive presence, the U.S. was able to take the lead again at the end of the third quarter with a steal and deep 3 from Stephen Curry.

The U.S. entered the fourth quarter with an 81-76 advantage, finishing the third with a Joel Embiid layup from a James no-look pass. After scoring only 20 points in the second quarter, the U.S. outscored South Sudan 37-18 in the third to regain footing in the game.

South Sudan pushed back against the U.S. throughout the fourth quarter, but the Americans held on to their lead until the final seconds, when JT Thor made a massive 3-pointer to take a 100-99 lead with 20 seconds remaining.

James then made his game-winning shot to give the U.S. a 101-100 lead. Some strong Team USA defense at the rim kept South Sudan from scoring, giving the U.S. the win — and the relief of knowing that they'd escaped the upset.

James led the team with 23 points, while South Sudan's Marial Shayok went 6 of 12 on 3-pointers for 25 points. Carlik Jones also earned a 15-point triple-double while leading the charge for South Sudan.

South Sudan's basketball team will be playing in its first-ever Olympics, and will face the U.S. again as part of Group C. Team USA will have to fend off the team for a second time in order to increase its hopes of a fifth consecutive gold.

The U.S., though, will hopefully have some extra help by then: Veteran forward Kevin Durant, who has missed four showcase games since being sidelined with a calf strain, is expected to play in Team USA's final exhibition, against Germany, on Monday.