Pablo Matera has been stripped of the Argentina captaincy and suspended along with two team-mates for "discriminatory and xenophobic" comments in historical social media posts.
The Argentine Rugby Union (UAR) says it "strongly repudiates" comments made by Matera as well as Guido Petti and Santiago Socino between 2011 and 2013.
The UAR said it met "urgently" after the posts resurfaced.
The trio were due to play Australia in the final Tri-Nations game on Saturday.
Matera, 27, who plays his club rugby for Stade Francais, has apologised and said he is "ashamed".
The UAR said "although the messages were expressed between 2011 and 2013" and did not represent the views shown by the trio during their time with the team, "it condemns any expression of hatred and we consider it unacceptable that those who express them represent our country".
The players' social media accounts were closed on Tuesday but screenshots of historical posts which disparaged black people and people from other South American nations circulated widely.
Flanker Matera has won 69 caps and led the Pumas to a famous victory over New Zealand on 14 November.
"I am very ashamed," he said.
"Sorry to all those who were offended by the barbarities that I wrote. At that time I never imagined who I was going to become. Today I have to own what I said nine years ago.
"I apologise also to my family and my team for what they are going through because of my actions and thanks to the people who love me for their support."
The UAR said it had requested that staff propose a new captain to the board of directors, while the players are suspended pending a "disciplinary process".