US diplomats have cast doubts on how much of a reliable partner Turkish Prime Minister Tayyip Erdogan is and portrayed its leadership as divided and permeated by Islamists, according to the German Der Spiegel magazine's website, citing leaked Wikileaks documents.According to the US diplomatic cables leaked by WikiLeaks, Erdogan was described as having "little understanding of politics beyond Ankara," Der Spiegel said.Erdogan had surrounded himself with an "iron ring of sycophantic (but contemptuous) advisors," the leaked cable suggested.