The decision to play South American World Cup qualifiers this month poses significant risks, the global footballers' union FIFPRO said on Friday as it warned that around 250 players face long-haul journeys amid the Covid-19 pandemic.
Two rounds of qualifying matches will be played between October 8 to October 13, featuring many of the world's top players, including Barcelona's Lionel Messi and Paris St Germain's Neymar who have been called up by Argentina and Brazil respectively.
Fifpro said that players should have the right to turn down a call-up without facing disciplinary action, adding that it would support players and challenge sanctions where necessary.
"Many players will be travelling in and out of countries with some of the highest incidence of COVID-19 pandemic, with more than 100 cases per 100,000 people," it said.
"There remain significant risks and legitimate concerns for players and their families and we maintain that all players must have a free choice to participate in national team activities or not."
Global soccer body FIFA confirmed on Thursday that clubs would be obliged to release players for the matches although it also imposed conditions, a move which was welcomed by Fifpro and the European Club Association (ECA).
FIFA said that players must be exempted from any travel or quarantine restrictions, both in the countries where they are due to play matches and in the country where their clubs are based, otherwise their clubs would not have to release them.
This potentially opened the door for clubs to withhold players although there were no immediate reports of withdrawals.
One source told Reuters that FIFA and Conmebol, the South American Confederation, were helping negotiate exemptions with public authorities.
Fifpro said that 30 of the 35 players named in Argentina's provisional squad play for clubs outside the country, while 33 out of 34 of Colombia's squad were based abroad along with the entire Paraguay and Uruguay squads.
Only Bolivia has a predominantly home-based squad.
However, Fifpro also called on clubs not to stand in the way of players who wanted to play.
"National team football is an important part of our game and players who wish to participate under the provided safeguards and regulations should be free to do so without interference," it said.