USA climbed out of a 16-point hole to beat South Sudan in a warm-up game that threatened to turn into an embarrassment.
The star-studded NBA team was booed by an expectant sell-out crowd during the first half at London's O2 Arena.
They were a massive 43.5-point favorite before the game and a defeat was almost unthinkable.
But USA fell 58-42 behind just before halftime before an almighty second-half fightback spared their blushes.
And even then they needed a late LeBron James bucket to steal a nerve-shredding 101-100 win.
When Joel Embiid turned the ball over midway through the second quarter, boos rang down from the stands.
South Sudan shot 62 per cent from the field in the first half and gave the US all they could handle with their aggressive defence.
The American team scored just one of their 12 three-point attempts in the first half.
But the team's two biggest stars Stephen Curry and James finally warmed up after the interval.
A 19-point swing in the third quarter powered by Curry and James turned things back in America's favor.
But they fell behind again 100-99 before James delivered the game winner.
The uncomfortable victory have left coach Steve Kerr with more questions than answers just days before the Olympics begin.
Their defense was much improved in the second half, but sparked by the backup unit rather than the starters.
USA has one more warm-up game - back in London against world champions Germany on Monday night.
Their first game in their quest for a fifth straight Olympic gold is on July 28 against Serbia.
They'll face this South Sudan team again in their second group game before taking on Puerto Rico in Lille, northern France.
More to follow...
USA basketball Olympic schedule
Men
July 28, 11.15am ET - USA vs Serbia, NBC
July 31, 3pm ET - USA vs South Sudan, USA Network
August 3, 11.15am ET - USA vs Puerto Rico, NBC
Women
July 29, 3pm ET, USA vs Japan, USA Network
August 1, 3pm ET, USA vs Belgium, USA Network
August 4, 11.15am ET USA vs Germany, USA Network