After slipping to 76-5 in pursuit of 195, a superb partnership worth 91 between Andries Gous and Harmeet Singh gave USA hope of a stunning victory.
As South Africa survives scare against USA, it was clear that they needed just 28 from 12 balls but the 19th over from Kagiso Rabada went for just two runs and included the wicket of Harmeet to drag the game back in South Africa’s favour.
The final over from Anrich Nortje went for just seven as South Africa held on for the win.
Gous ended unbeaten on 80 after a brilliant knock that included five fours and five sixes, while Rabada was the pick of the Proteas bowlers taking 3-18.
Quinton de Kock earlier top-scored for South Africa with a sublime 74 from 40 balls, with seven fours and five sixes.
Skipper Aiden Markram added a lively 46 from 32 balls and Heinrich Klaasen 36 from 22 as South Africa posted 194-4 – their highest score of the tournament so far.
South Africa went into the game with four wins from four but their batters have struggled for fluency, with their top score in the group stage just 115.
The tricky pitch in New York, where they played three of their four group games, offers some mitigation and the more batter-friendly surface in Antigua allowed them to demonstrate the firepower in their top order.
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Despite losing Reeza Hendricks early on De Kock and Markram took control, reaching 64-1 at the end of the powerplay that included a brutal 28 runs off a Jessy Singh over.
South Africa looked on course for a score in excess of 200 at that stage but USA continued to display the admirable spirit they have shown throughout this tournament.
Harmeet removed De Kock and David Miller in successive deliveries to check momentum, while left-armer Saurabh Netravalkar once again impressed with figures of 2-21.
USA chased down 195 in their opener against Canada and they began aggressively to try and keep up with the rate, but lost wickets at regular intervals, slipping from 53-1 to 76-5.
That brought Gous to the crease to join Harmeet with the game seemingly gone, but some extraordinary hitting brought them back into contention.
Gous, who is now the tournament’s top run-scorer with 182, reached his half-century from just 33 balls with two huge back-to-back sixes off Nortje.
He then hit two more in the 18th over from Tabraiz Shamsi that went for 22.
But Harmeet holed out to Tristan Stubbs at the start of the next over from Rabada, who showed all his class at the death to snuff out the USA’s challenge.
‘USA put us under pressure’ – what they said
Man of the match, South Africa’s Quinton de Kock: “It is nice getting out on an easier wicket finally. We’ve had some tricky wickets coming up to this game so it was nice to get some time out in the middle. The boys played nicely and so did Team USA. They put us under pressure, particularly towards the end. It was a great game.”
South Africa captain Aiden Markram: “You are always going to feel like you should score more. It was a nice start but the wicket definitely changes up. It got slower and more stoppy. If you marry those things together it makes sense why you don’t feel like you a bang. We’d rather finish like that than blow out for 160-170.”
USA captain Aaron Jones: “I don’t want to say disappointed, but yeah it’s hard to take the defeat after getting so close. I thought we could have been more disciplined bowling-wise.
“We have a really good unit, a lot of talent in the USA. When we play good cricket we can beat any team in the world.”
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