Second-half goals from Jair Reinoso and Raul Castro gave Bolivian giants The Strongest the advantage after a 2-0 win over Defensor Sporting in the first leg of their last-16 Copa Libertadores clash.
The reigning Bolivian champions largely dominated proceedings against their Uruguayan opponents but had to wait until the 68th minute to break the deadlock, when forward Reinoso headed home from Pablo Escobar's long ball.
Midfielder Castro doubled their advantage with a low shot from outside the box 10 minutes later to put The Strongest in pole position to qualify for the quarter-finals.
"We needed to win and maintain the zero in our goal," said Escobar.
"They are a great squad, they do not give you a lot of space to place so it is very hard to play against.
"We have won the 50 per cent of the game, now we have to defend the result in their home."