Besong said: "Yes, obviously he’s very frustrated with how long it’s taken. But he’s a professional and anticipates these things.
"I spoke to him about a week ago and he is very calm with everything that is going on. But of course, he’s already told them he wants to go to United.
"He just wanted the two clubs to find an agreement, as he’s very grateful for the opportunity that he’s been given by Brentford in his career."