A second-half header from Andre Lima earned Gremio a 1-0 victory over Brazilian rivals Coritiba in the first leg of their Copa Sudamericana first-round tie.
Copa Sudamericana: Iquique 2-0 Nacional
Both teams struggled to create opportunities under heavy rain at Porto Alegre's Estadio Olimpico, but Lima broke the deadlock 20 minutes from time when he connected with substitute Leo Gago's free-kick to nod home.
Coritiba's coach Marcelo Oliveira was furious the match was allowed to go ahead, but backed his side to overturn the one-goal deficit.
"We shouldn't have played this match,'' he said. "The field was in awful conditions. Anyway, we are confident we can recover at home.''
Gremio, competing in the tournament for the fifth time, have been eliminated at the first hurdle in each of the four previous occasions and will look to end that run at the Estadio Couto Pereira on August 23.
Meanwhile, in Chile, hosts Deportes Iquique took a big step towards progressing as they beat Uruguayan team Nacional 2-0 thanks to goals from Sebastian Ereros and Misael Avila.
The sides will meet again in the second leg at Montevideo's Estadio Centenario on August 14.
Elsewhere, Ecuadorian outfit Emelec overcame Peruvian team Universidad San Martin 1-0 at home, Efren Mera netting the game's only goal 25 minutes from time when he pounced on the rebound from close range after good work by Enner Valencia. Gustavo Quinteros' men will look to finish the job in Lima on August 21.
Colombian side Deportes Tolima took the upper hand against Deportivo Lara of Venezuela with a 3-1 home win. Paraguayan striker Robin Ramirez opened the scoring with a powerful long-range shot five minutes before the interval and Jair Arrechea doubled their advantage two minutes later.
Jose Torrealba gave the visitors hope soon after the break but Carlos Preciado restored the hosts' two-goal cushion with a third goal midway through the second half. The second leg will take place at the Estadio Metropolitano Cabudare de Lara on August 16.
Finally, in Peru, Colombian side Envigado secured a 0-0 draw against Union Comercio, leaving the tie finely poised for the second leg in Antioquia on August 15.