Germany\'s foreign minister summoned the U.S. ambassador Thursday to discuss allegations the United States tapped Chancellor Angela Merkel\'s conversations. Guido Westerwelle summoned Ambassador John Emerson to Berlin to meet following reports Wednesday the United States was monitoring Merkel\'s cellphone conversations, Spiegel Online reported. Foreign Ministry sources told Spiegel Online Westerwelle is expected to stress the \"incomprehension and outrage\" over the reported monitoring of a close ally and partner. The White House said Wednesday President Obama and Merkel discussed reports the United States monitored Merkel\'s communications and the president assured the chancellor the United States \"is not and will not\" monitor her communications. Der Spiegel reported the surveillance, based on a review by the Federal Intelligence Service and the Federal Office for Security in Information Technology. A National Security Council spokeswoman told Der Spiegel Obama assured Merkel \"the United States does not monitor\" her communications, but the publication noted the U.S. spokeswoman did not say whether the denial applies to possible past surveillance.