The Guardian newspaper reports that White House, Pentagon and State Department officials confirm the United States spied on the phone conversations of 35 world leaders.
The latest report comes as European leaders have united behind a furious Germany to denounce the United States for allegations it spied on its allies.
White House spokesman Jay Carney refused Thursday to deny the U.S. National Security Agency had spied on past communications from German Chancellor Angela Merkel.
Ms. Merkel says she made it clear in a phone call Wednesday to U.S. President Barack Obama that "spying on friends is not acceptable at all."
Before a 28-nation European Union summit meeting in Brussels, Ms. Merkel said, "We need trust among allies and partners. Such trust now has to be built anew."
Other European leaders arriving for the meeting echoed the German leader's displeasure.
European Union Commission President Jose Manuel Barroso objected to the the spying as a slide toward "totalitarianism."
Early Thursday, Germany's foreign minister summoned the U.S. ambassador to discuss the matter.
The Obama administration has denied news reports about many U.S. intelligence activities. It has faced a firestorm of criticism over new revelations that it has spied on its allies. Those reports stem from secret documents leaked by NSA contractor Edward Snowden, who is living in Russia.
White House officials have repeatedly said the intelligence gathered by the United States is the typically "gathered by all nations."
President Obama has ordered a review of the way U.S. intelligence is gathered, in an effort he says is intended to ensure a proper balance of security concerns and privacy concerns.