Werner Kok scored a late try to help the Blitzboks pull off a 21-19 victory over New Zealand in the Hong Kong Sevens quarter-final on Sunday.
The South Africans will now take on USA in the second Cup semi-final at 9.53am SA time, while Australia and Fiji will lock horns in the first semi at 9.31am.
After Chris Dry had opened the scoring for the Blitzboks after two minutes, New Zealand took charge as Regan Ware and Sione Molia dotted down before halftime to put the Kiwis 12-7 ahead.
Dylan Sage was also yellow-carded for a high tackle, and it looked like the Blitzboks were in danger of being knocked out of the Hong Kong tournament again.
But Cecil Afrika raced over from a set move early in the second half to put his team in front at 14-12, and with less than a minute left on the clock, Kok pounced at a ruck for the decisive play that needed approval from the TMO.
The angled conversion from Afrika was crucial as it meant that the Springbok Sevens were nine points ahead with just a few seconds to go.
So even when Sam Dickson scored and Beaudein Waaka slotted the touchline conversion after the hooter, it was in vain as the South Africans went through to the last-four.
@wernerkok1 on the try that secured the 21-19 win over @nz7s and book a place in the Cup semis against @USARugby @OfficialHK7s. pic.twitter.com/v94JSjVDz2