The second semifinal between Argentina and Colombia is on Tuesday.
"I want Argentina, I am cheering them on," Neymar said with a smile. "I have friends there and in the final Brazil will win."
The last time the two sides met in a Copa America final was in 2007, when Brazil won 3-0 in Venezuela, and a title match between the arch rivals would be a treat for the neutrals.
It would not only pit the tournament's only unbeaten teams against each other it would also be a showdown between two of the best No. 10s in the game, former Barcelona teammates Neymar and Lionel Messi.
Both players have had an exceptional tournament so far, with Neymar recording two goals and three assists, while Messi has four goals and four assists.
Brazil are reigning champions and have home advantage at a tournament that was supposed to be co-hosted by Argentina and Colombia.
Colombia was stripped of hosting rights due to a wave of civil unrest and Argentina pulled out at the last minute because of a surge in COVID-19 cases.
Neymar missed Brazil's Copa America triumph on home soil two years ago but inspired them to the 2013 Confederations Cup as well as Olympic gold in Rio de Janeiro in 2016.
Messi, meanwhile, has won everything with his club Barcelona but no senior title with Argentina, who are aiming to win a first major trophy since the 1993 Copa America.