Argentina prepared for the knockout stages of the Rugby World Cup with an emphatic 64-19 win over Pool C minnow Namibia in Leicester.

The Pumas were guaranteed progression prior to Monday's (AEDT) clash at the King Power Stadium and ran in nine tries to keep a gutsy but limited Namibia side winless in World Cup competition.

Juan Martin Hernandez was given a rare start at fly-half and, aside from Namibia tries through Johan Tromp, JC Greyling and Eugene Jantjies, his opener paved the way for Pumas dominance.

While sloppy mistakes largely went unpunished by Namibia, Matias Moroni went over himself and assisted Horacio Agulla to give Argentina a 29-point half-time lead.

After Greyling's effort, Matias Alemanno and Leonardo Senatore scored the pick of Argentina's four second-half tries, as it awaits Ireland or France in the next round while Namibia contemplates a new era without retired captain Jacques Burger.

Hernandez was involved from the off as Argentina spurned the first chance to lead when Santiago Gonzalez kicked a penalty wide.

Just a minute later, the number 10 collected Moroni's pass after a jinking run down the right before touching down - Gonzalez making amends with the boot - with Greyling's yellow card for clattering Hernandez making life more difficult for Namibia.

Tromp made the most of an overly elaborate pass in the middle to reduce the arrears with the help of a conversion but Moroni was back in the thick of things six minutes later when he recorded Argentina's second try with persistence and some loose Namibia tackling.

A quick switch to the left allowed Agulla to extend Argentina's lead - after a review cleared the suggestion of blocking in the build-up - as Argentina's wingers continued to pose problems.

Lucas Gonzalez Amorosino was denied a stunning virtuoso try after a run from his own 22 by a Johan Deysel tackle as Argentina finished the half strongly with late scores from Facundo Isla and Lucas Noguera Paz.

Namibia went over again four minutes into the second half as Greyling seized on loose handling from Paz and surged for the line - Theuns Kotze adding the extras - although it offered fleeting respite as Alemanno went over five minutes later, allowing World Cup debutant Juan Pablo Socino to kick the conversion. 

While Namibia grew in confidence prior to the hour - aided slightly by Marcelo Bosch's sin-bin for a tip-tackle - Argentina made the most of tired legs with Socino converting tries from Senatore, Julian Montoya and substitute Tomas Cubelli.

Namibia finished the game with 14 men as Tinus du Plessis was unfortunate to see yellow after contesting a high ball with Bosch.

However, Jantjies salvaged Namibian pride late on while prop Johnny Redelinghuys's failed conversion raised smiles, as Argentina looks ahead to tougher tests.