QPR boss Neil Warnock says his own situation is affecting their transfer plans.
Warnock revealed that doubts over his future at Loftus Road have damaged his transfer plans this summer.
Moves for Craig Mackail-Smith and Danny Graham failed because of fears that Warnock would leave.
Manager Warnock said: "I spoke to Craig and Danny, and they were both concerned about my position at that time."
A price has been agreed for Campbell but Warnock said: "We couldn't agree certain fees with his advisors, so at the moment it's on ice."