The White House says President Barack Obama has assured German Chancellor Angela Merkel that the U.S. National Security Agency is not listening in on her phone calls.

The two leaders spoke over the phone Wednesday after Merkel learned U.S. intelligence may have targeted her mobile phone, and said that would be "a serious breach of trust" if confirmed, her government said in a statement.

White House spokesman Jay Carney denied the NSA is listening in on Merkel's calls.

The German government initiated the phone call between Merkel and Obama after receiving "information that the chancellor's cellphone may be monitored" by U.S. intelligence, according to a statement released by Merkel's office. It wouldn't elaborate but German news magazine Der Spiegel, which has published material from NSA leaker Edward Snowden, said its research triggered the response.

Merkel spokesman Steffen Seibert said in a statement the chancellor made clear to Obama in a phone call that "she views such practices, if the indications are confirmed ... as completely unacceptable."

Merkel said among close partners such as Germany and the U.S., "there must not be such surveillance of a head of government's communication," Seibert added. "That would be a serious breach of trust. Such practices must be stopped immediately."

In Washington, Carney said "the United States is not monitoring and will not monitor the communications of the chancellor."

Germany New Govermnent

The German government initiated the phone call between Barack Obama and Angela Merkel after Germany received "information that the chancellor's cellphone may be monitored" by U.S. intelligence. (Michael Sohn/Associated Press)

Merkel raised concerns over electronic eavesdropping issues when Obama visited Germany in June and demanded answers from the U.S. government and called for greater European data protection.

However, Wednesday's statement was much more sharply worded and appeared to reflect frustration over the answers provided so far by the U.S. government.

Merkel called for U.S. authorities to clarify the extent of surveillance in Germany and to provide answers to "questions that the German government asked months ago," Seibert said.

Carney says the U.S. is examining Germany's concerns as part of a review of how the U.S. gathers intelligence. The White House has cited that review in responding to similar spying concerns from France and other U.S. allies.

Readout of the President’s Phone Call with Chancellor Merkel of Germany

Today, President Obama and Chancellor Merkel spoke by telephone regarding allegations that the U.S. National Security Agency intercepted the communications of the German Chancellor. The President assured the Chancellor that the United States is not monitoring and will not monitor the communications of Chancellor Merkel.

The United States greatly values our close cooperation with Germany on a broad range of shared security challenges. As the President has said, the United States is reviewing the way that we gather intelligence to ensure that we properly balance the security concerns of our citizens and allies with the privacy concerns that all people share.

Both leaders agreed to intensify further the cooperation between our intelligence services with the goal of protecting the security of both countries and of our partners, as well as protecting the privacy of our citizens. 

-White House Press Secretary