FIJI's John Stewart was sin-binned as a last-gasp penalty gave Argentina a semi-final berth at the South Africa Sevens.
Playmaker Joji Raqamate scored and narrowed the deficit to 7-12 after a lack-lustre first-half performance .
Setefano Cakau scored Fiji's second try in the corner but Ilai Tinai missed the conversion for a 12-12 draw.
All was lost when Fiji gave away possession and tackled poorly when the Argentinians struck back.
With a minute to go, Stewart was yellow carded and the penalty became the difference, 15-12.