The Red Devils have been heavily linked with a move for the Spain defender in recent days as Louis van Gaal looks to bolster his defensive options by looking to sign the Real Madrid centre-half.
United are thought to have made their interest in signing Ramos concrete over the last few days, with some reports suggesting that a deal could involve goalkeeper David De Gea heading in the other direction.
However, Barcelona star Iniesta, who is an international team-mate of the defender, does not expect Real Madrid to be willing to let Ramos leave the club this summer.
Iniesta told Marca: “I’ve always said that Ramos is one of the best centre-backs in the world.
“I don’t think they’ll let him go.”
Ramos has won three La Liga titles, three Copa del Rey crowns and the Champions League.
The Real Madrid defender is set to become a free agent in the summer of 2017 unless the World Cup winner agrees a new deal with the 10-time European champions.
The World Cup winner scored four goals in 42 games in all competitions for Los Blancos last term.
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