The former Manchester United and West Ham shot-stopper has been the deputy to Allan McGregor at Ibrox since joining on a free transfer in the summer.
Derby manager Paul Jewell confirmed: "The (Derby) chairman spoke to his agent. I´ve spoken to (Rangers boss) Walter Smith. I´ve been in contact with Walter for quite a while now. Hopefully we can get that underlined, if not Wednesday, then Thursday."
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