US ambassador John Phillips was called in "for clarification on the media reports that allege Italian leader Silvio Berlusconi and some of his close associates were subjected to wiretapping in 2011," it said in a brief statement.
According to Italy's La Repubblica and Germany's Sueddeutsche Zeitung, classified documents released by WikiLeaks reveal the National Security Agency (NSA) spied on leaders from German Chancellor Angela Merkel to UN Secretary General Ban Ki-moon, as well as the party-loving Italian billionaire.
Among the WikiLeaks documents were details of a 2011 meeting Merkel held with Berlusconi and then French president Nicolas Sarkozy.
In the meeting Merkel and Sarkozy pressured Berlusconi to reduce public debt and strengthen Italy's banking sector.
The meeting was tense and unfriendly, according to a Berlusconi advisor, who was painted by the newspapers as the probable target through whom the NSA obtained the information.
Another document showed the NSA listened in on talks between Berlusconi and Israeli Prime Minister Benjamin Netanyahu, in which Netanyahu asked Berlusconi to help him improve relations with Washington that were strained by plans for Jewish settlements in East Jerusalem.