Cardiff City chairman Peter Ridsdale said: "We don't want to sell anybody and our key players are not for sale at any price. I really mean that.
"Our aim is to earn promotion and we have virtually all of our key players on long-term contracts.
"We want Glenn to stay and there is a new offer on the table.
"But he has not signed it yet and that is the only reason we may - and I stress may - talk to clubs if their offer is acceptable."