US diplomats refer to Russian President Dmitry Medvedev as a hesitant leader and Prime Minister Vladimir Putin as an "alpha male," Kommersant reported today, citing documents released by WikiLeaks.

The respected business daily said the relevant WikiLeaks documents were obtained by Germany's Der Spiegel weekly and released on a private Twitter account.

"The Americans call the Russian President Dmitry Medvedev pale and hesitant, and Prime Minister Vladimir Putin an alpha male," the newspaper wrote.

Kommersant cited a Kremlin source as saying that Washington had warned Moscow that the website would release information that was damaging to Russia-US relations and that officials here were prepared for the news.

"Our own diplomats are sometimes just as open in their own private messages to each other," the unidentified Kremlin official was quoted as saying.

Putin's spokesman meanwhile told the daily that it was premature to take the reported character portraits too seriously.

"We have to wait and see what level of diplomats made these comments, and in what documents they appear," spokesman Dmitry Peskov told the daily.

"And anyway, we have to find out if it is actually Putin they are talking about," Peskov added.