Germany is sending intelligence officials to Washington to discuss allegations of U.S. spying on German mobile phones, including one used by Chancellor Angela Merkel.
German newspaper Bild am Sonntag quoted Interior Minister Hans-Peter Friedrich Sunday as saying the allegations have "shaken" Berlin's trust in Washington, a longtime ally.
Friedrich told the newspaper that "if the Americans intercepted mobile phone communications in Germany, they broke German law" and said that would be an "unacceptable violation of German sovereignty."
Bild am Sonntag quoted an unnamed official of the U.S. National Security Agency as saying President Barack Obama received an NSA briefing in 2010, informing him that U.S. spies were monitoring Chancellor Merkel's mobile communications.
The newspaper's source said Obama let the operation continue.
Merkel complained about the alleged NSA surveillance of her communications in a phone call to Obama on Wednesday. Her office said she told Obama that if such practices occurred, they represent a "grave breach of trust."
The White House said it is not monitoring Merkel's mobile phones and will not do so in future. But, it did not comment on whether the NSA spied on her devices in the past.
The Bild am Sonntag report said the NSA allegedly bugged a mobile phone used by Merkel to conduct the business of her Christian Democratic Union party and a second supposedly secure device that she began using in the middle of this year.
The newspaper said the only Merkel phone that the NSA could not access was the land line in her office.
In a separate report on Saturday, German weekly Der Spiegel said the NSA may have been bugging Merkel's mobile phone as early as 2002, when she served as opposition leader. She took office as chancellor in 2005.
Former NSA contractor Edward Snowden leaked documents earlier this year purporting to show sweeping U.S. surveillance of Internet searches and telephone records of U.S. citizens and world leaders. The revelations have sparked outrage globally.
Germany is working with Brazil on a draft UN General Assembly resolution to guarantee privacy in electronic communications. UN diplomats say it would call for extending the International Covenant on Civil and Political Rights to Internet activities, but would not mention the United States.