Leto now needs a work permit to play in the UK but has been denied one by the Department of Work and Pensions to the annoyance of Rafael Benitez.
"I am disappointed and it was a surprise because this is a player who has played in the Champions League and been in the Argentina squad for the Olympic Games. You have managers talking about how good he is, so I think the system needs to change," said the Reds boss.
"Now we have to look for a solution, maybe find a team for him on loan, but we have maybe eight or 10 teams in Spain, Italy and Greece asking about him. When you have eight or 10 teams asking about a player and he's not playing, it means that he is good.
"But maybe there is another vision of football."