The Reds' number two is keen not to comment on media speculation that Ronaldo will join Real Madrid, but insists United is the best place for the winger to be next season.
"Manchester United is very special," Queiroz told Portuguese radio station Renascenca. "Because of that we know how to surround Cristiano completely with all the affection and all the attention he deserves.
"However, not speaking is the most sensible course of action at this moment, so that we don't contribute to a less than positive spectacle and so we don't aid those whose interests are difficult to identify."
Queiroz has also been linked with the Portugal coaching job vacated by Luis Felipe Scolari, but refused to declare his interest in the post.
"I'm not going to put myself in the market because the decision on the national coach should not be a result of those who make themselves candidates, but a decision that is conscious, rational and based on what the Federation judges [believe] is necessary for the team.
"I'm not going to tell you whether or not I'm contacted, that way I know for sure that it will be dealt with in due form and in due place."