"When the head is rotten, it affects the whole body," King Abdullah was quoted as saying by the New York Times in leaked US diplomatic cables.
Zardari is reportedly unpopular at home and has spent 11 years in jail on charges ranging from corruption to murder, but has never been convicted.
A spokesman for the President, who is currently on a visit to Sri Lanka has dismissed the reported insult, saying that Zardari considers King Abdullah his "elder brother".
"The so called leaks are attempt to create misperceptions between two brotherly Islamic countries.
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