Thousands of US diplomatic messages leaked on Sunday offered an unflattering view of key allies, with Russian Prime Minister Vladimir Putin mockingly termed the "alpha dog" by one of the cables.
Copies of the German news weekly Der Spiegel went on sale in railway stations hours before an embargo imposed by a consortium of news media was due to run out.
Quotes from the more than 250,000 cables obtained by the Wikileaks website were also circulating on the Twitter web service in advance.
The confidential assessments by US diplomats said for example that Afghan President Hamid Karzai was a "weak personality" who was "driven by paranoia" and "conspiracy theories".
The accounts of Turkish Prime Minister Recep Tayyip Erdogan were suspicious of him, while remarks about Kenya's leadership were contemptuous.
One exchange indicated the State Department in Washington asked the US embassy in Rome to check rumours that Prime Minister Silvio Berlusconi had private property dealings with Putin. Russian President Dmitry Medvedev was termed "pale, hesitant".
In an assessment of German Chancellor Angela Merkel, a diplomat marked her: "Avoids risk, not very creative."
Spiegel said 90 percent of the material involved the period from 2005 onwards. Only six percent was labelled "secret". Other media which had sifted and edited the material and were set to publish it included the New York Times and the London newspaper The Guardian.