Former Pumas captain Agustín Pichot announced on Sunday that he would challenge England's Bill Beaumont to lead World Rugby.
"This is a critical election at a critical time for Rugby." the ex-Argentina star said in a tweet announcing he would run for the position of chairman in this month's election.
Pichot, 45, retired as a player in 2009. He has served under Beaumont as a vice-chairman of World Rugby since 2016.
A scrum half, Pichot won 71 caps for the Pumas and played club rugby in Europe for Bristol and the two Paris clubs: Stade Français and Racing.
"It's time to change, to focus our attention, love and dedication to all Unions and federations equally," he wrote in a manifesto attached to the tweet.
"We all fight for and believe in a fair, equal and more inclusive world," he wrote, going on to promise to "support both established and emerging unions" to make them "competitive and strong."
"The current crisis is an opportunity for the global realignment of our game," he wrote.
Pichot proposes reforming rugby's calendar. He said he tried and failed as vice-president and, in an interview published on Sunday, blamed Beaumont.
"We really had to take action to change the world calendar, I felt a lot of resistance from Bill," Pichot told French sports daily L'Equipe.
"We think differently," Pichot said of Beaumont.
Beaumont is running with the president of the French Federation, Bernard Laporte, as his candidate for vice-chairman.
Pichot said he is running "alone."
The election is due to take place on April 26 by an electronic vote with an announcement of the results on May 12.