Argentinian giants River Plate beat Guarani of Paraguay 2-0 here Tuesday to put themselves firmly on course for a place in the final of the Copa Libertadores.

Second-half goals from defender Gabriel Mercado and Rodrigo Mora gave the Buenos Aires side a commanding first-leg lead, which leaves Guarani needing to stage a dramatic fightback to advance to the final.

Mercado fired River into the lead on 59 minutes before Uruguayan striker Mora made it 2-0 in the 72nd minute.

Mora's goal was a contender for goal of the tournament, with the 27-year-old advancing into the Guarani penalty area before lifting a sublime chip over goalkeeper Alfredo Aguilar.

Earlier Mercado had broken Guarani's resistance, lashing home from close range after the Paraguayans failed to deal with a deep ball into the penalty area.

The second Copa Libertadores semi-final will see Internacional of Brazil face Mexican side Tigres in Porto Alegre.