Paraguay's Marcelo Perez (left) and Brazil's Lucas Fasson jump to head the ball during the Venezuela 2024 CONMEBOL Pre-Olympic Tournament football match between Brazil and Paraguay at the Brigido Iriarte stadium in Caracas on Feb 5, 2024. (PHOTO / AFP)

Olympic champions Brazil suffered a setback in their bid to secure a place at this year's Paris Games after their under-23 team slumped to a shock 1-0 defeat by Paraguay on Monday in the final four South American qualifying tournament.

Brazil, Paraguay, Argentina and Venezuela are competing in a round robin final qualifying stage for the 2024 Games, with only the top two securing berths in Paris.

Fabrizio Peralta's header in the final seconds of the first half was enough to give Paraguay, who last competed at the Olympics in 2004, an unexpected victory.

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Brazil's teenage prodigy Endrick, who will join Real Madrid later this year, squandered a chance to put the 2020 Tokyo Games gold medallists ahead when he missed a penalty after 29 minutes.

Brazil's Gabriel Pec jumps over Paraguay's Gilberto Flores during South America's under-23 pre-Olympic tournament soccer match at Brigido Iriarte stadium in Caracas, Venezuela, on Feb 5, 2024. (PHOTO / AP)

In a later qualifying game, a last-gasp penalty from substitute Kevin Kelsy snatched a 2-2 draw for Venezuela against Argentina.

Javier Mascherano's side finished the game with nine men after Valentin Barco and Gonzalo Lujan were sent off, while Venezuela's Bryant Ortega also received a red card.

Brazil will next face Venezuela, who beat them 3-1 in the preliminary stage earlier this month, on Thursday. Paraguay's next fixture will be against Argentina.

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The qualifiers, being held in Caracas, wrap up on Feb 11.