The Juventus skipper who led Azzurri to Euro 2020 glory last summer, will depart the national team following their clash with CONMEBOL Copa America 2021 champions Argentina on June 1.
This year will mark the first time the world's oldest international football tournament is staged in two countries.
Belloso said the contrasting trends of the pandemic among South American nations and regions posed a major challenge to CONMEBOL's efforts.
FIFA has allowed teams to have up to five substitutions per game, instead of three that was there before, as a temporary measure to help cope with potential fixture congestion.
The first two rounds need to be rearranged but CONMEBOL said any new dates would have to be ratified by FIFA.
Meanwhile, FIFA on Thursday decided to postpone the Club World Cup in 2021 to accommodate the Euro and Copa America during that time period.
The 12-team tournament follows the 16th edition of the Euros which also has been postponed to 2021 amidst the crisis unleashed by the spread of COVID-19.
The letter said it expressed the position of its 10 members: Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay and Venezuela.
The sentences form part of a global crackdown by authorities on corruption in football, which has snared some of the game's top officials.
Messi has been handed over this ban after the veteran had accused CONMEBOL of "corruption" during the Copa America tournament which Brazil went on to win.
