Der Spiegel is reporting a dramatic confrontation between German Chancellor Angela Merkel and President Obama today, as Chancellor Merkel called the president to warn of "a serious breach of trust" if evidence surfaces that her personal cell phone was monitored by American intelligence agencies. A German government spokesman told the AP that the government, "has received information that the chancellor's cellphone may be monitored by American intelligence." That information has not been published, but German intelligence and IT security services reportedly investigated the claims, which allege many years of sustained surveillance, and found them plausible enough to justify Merkel's immediate and urgent response. Along with the warning, Chancellor Merkel asked for "immediate and comprehensive clarification" on the state of US surveillance on her personal communication.
President Obama was quick to deny the reports, saying the US "is not monitoring and will not monitor" the German chancellor, although he did not explicitly deny past surveillance. The reports are consistent with earlier revelations that the NSA had hacked into Mexican president Felipe Calderon's email as well as widespread phone surveillance in France, establishing a pattern of US surveillance on allied governments.
Update: The White House has released a further statement on the President's call with 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."