Brazil supporters have lacked interest in this year's tournament due to the COVID-19 pandemic in the nation and last-minute changes which saw Brazil host the Copa after CONMEBOL announced Argentina and Colombia would no longer stage the event.
Brazilian SporTV journalist Fabiola Andrade is among those fans that have publicly come out to support Argentina in the final.
Andrade explained her controversial decision on Instagram and wrote: "Before stoning me in a public square, let me explain: I love Brazil, Brazilian football...I have several Argentine friends. But I'm not going to root for Argentina in the Copa America final because of them, no. I cheer because I love #football and @leomessi This guy needs to win a title with his country's shirt! For justice!"
Messi, 34, is the leading scorer in the competition with four goals and has also set up five more. The forward is also looking to win his first major international competition for Argentina having failed in four attempts.
"What I want most is to win a title with the national team," Messi said after Argentina beat Colombia in a semifinal penalty shootout. "We are more eager than ever to win the Copa."
The Paris Saint-Germain forward, who missed Brazil's 2019 Copa triumph on home soil due to injury, is shocked that some compatriots would even consider supporting eternal rivals Argentina.
Neymar wrote on Instagram: "I am 'Brazilian with a lot of pride and with a lot of love. My dream was always to be in the Brazilian team and hear the fans singing. I never attacked nor would I ever attack Brazil if they are playing for something, whatever the sport, a model [beauty] contest, the Oscar......... I am Brazil, and who is Brazilian and does it differently?"
Neymar then added: "OK, I'll respect [that], but go to ---," using an expletive word to finish the sentence.
Brazil defender Marquinhos has also urged fans to show more support ahead of the final.
"It is difficult [the situation], because we see so many Brazilians, so many people in the press who are against and simply do not support the Brazilian team, who have no pleasure and pride in seeing the team, in rooting for us," the PSG player said.
"The fans, the journalists, the Brazilian people, no matter how difficult the moment we are living, could send positive energy, a good energy, because the national team is a source of pride for the Brazilian fans.
"From our part, we have tried to represent the team and the fans in the best possible way, giving everything on the pitch and that's what we've been doing at the Copa America."
Brazil are aiming for their sixth Copa title since 1997 while Argentina have not lifted the title since 1993.
In a tournament that was played out with no fans due to the pandemic, Rio de Janeiro officials announced on Friday that it will allow limited attendance at the final with 6,500 spectators, or 10% of the famed stadium's capacity, allowed to watch in person.