Cardiff chairman Peter Ridsdale told the Western Mail: "We have offered Glenn a three-year deal, he has not signed it yet and it could be a situation which might run for a while.
"We have had interest from two other clubs in the Championship, but Glenn would not entertain that. He says he will not play for any other Championship side because he loves Cardiff too much. There has been no approach from any side in the Premiership yet.
"I think Glenn is a very good player and I want him to stay, but, if there is an offer Glenn feels is too good to turn down and which we feel is too good to refuse, then things do change - I want Glenn to stay and I want him to play in the Premiership with Cardiff."