The centre-back, 25, was expected to thrash out personal terms and undergo a medical, with a view to finalising the deal in the next 24 hours.
Cuellar first caught the eye of Rangers manager Walter Smith during last season´s UEFA Cup campaign, when the Ibrox side exited the competition at the hands of Osasuna, and the 6ft 3in defender will become the sixth permanent signing of the summer for Rangers.
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