Cerro Porteno beat Deportivo Petare 1-0 in the first leg of their Copa Libertadores first-round qualifying match on Thursday.
Paraguayan hosts Cerro were in control throughout but had to wait until the 70th minute before Roberto Nanni gave them a deserved lead at the Estadio Defensores del Chaco.
They should have gone in front early on in Asuncion when Luis Cardozo failed to score with an open goal from just six yards out.
Cerro continued to press and went close again when Jorge Nunez’s free-kick was kept out by goalkeeper Alan Liebeskind.
Liebeskind saved the Venezuelan visitors again in the 35th minute, palming away Juan Lucero’s long-range effort.
The away side barely had a sight of goal throughout the first half.
And when a rare opportunity finally came, Victor Guaza wasn’t able to direct his header goalwards.
Petare threatened again just after the restart, but Feliz Casseres saw his header saved by Diego Barretto.
Even if he had found the net, the linesman’s flag would have ruled out the strike for offside.
Cerro soon regained control and Nunez forced another smart save from Liebeskind.
With 20 minutes remaining, the hosts finally found the breakthrough, with Nanni on hand to power home what proved to be the winning goal.
Deportivo rarely looked like mounting a comeback and they could have gone 2-0 down when goal-scorer Nanni went close with another powerful header late on.
Despite their dominance, the Paraguayans were forced to settle for a slender advantage going into the second leg in Venezuela on February 3.
Elsewhere, Chilean club Union Espanola came away from Bolivia’s Bolivar with a valuable 1-0 win in the first leg of their first-round qualifier.
Left midfielder Fernando Cordero scored the winner for the visitors in the 17th minute at La Paz’s Estadio Hernando Siles.
The away goal makes them slight favourites to progress after the return leg at the Estadio Santa Laura-Universidad SEK in Santiago, also on February 3.