The United States came from 16 points down to avoid one of the biggest shocks in basketball history in a dramatic 101-100 victory over South Sudan in London.

South Sudan led 58-42 in the second quarter before taking a 14-point lead into the break in an Olympics warm-up game at the O2 Arena.

The USA went on a 16-0 run to end the third quarter with a five-point lead but South Sudan battled back to go one point ahead with 20 seconds remaining.

LeBron James hit a crucial lay-up to put his side ahead by one point with eight seconds to go, and South Sudan could not hit a late winner.

The USA are targeting a fifth consecutive men's basketball gold medal at this summer's Olympics in Paris, while South Sudan, ranked 33rd in the world, will play in their first Games.

The 12-man USA roster is filled with some of the NBA's greatest talents, while only four of the South Sudan team have played an NBA game.

But they outplayed the world number one side in the first half, hitting 61% of their shots, while the USA only made one three-pointer.

Marial Shayok scored a game-high 25 points for South Sudan and Charlotte Hornets forward JT Thor hit a three-pointer to put his side 100-99 ahead late on.

But the USA were indebted to James, who capped a fine second-half showing with the game-winner to finish with 23 points.

The United States have won all four of their pre-Olympic exhibition games, with their final warm-up coming against Germany at the O2 on Monday.

"That was better than the blowouts, at least we got tested - I like getting tested baby," said two-time Olympic champion James, 39.

The USA and South Sudan will face each other in Group C of the 2024 Olympics on 31 July.

"The match was super important because we feel like we can’t be beaten and they showed us we can be beat," said USA guard Anthony Edwards.

"We have to come ready to play."