United boss Sir Alex Ferguson has expressed interest in both 20 year-olds and Perrin said: "These two players have already declared that they are not the best friends in the world.
"I will speak to them, but these are matters between men. They are not linked to a problem in the game. It's their private life, their personal life."
Ferguson was understandably impressed with what Benzema did in scoring against his team two weeks ago but will care little for talk of this behaviour.
United won the Champions League almost nine years ago with two forwards - Teddy Sheringham and Andy Cole - who did not speak to each other.