Germany asked the top US intelligence official at the Berlin embassy on Thursday to leave the country, a highly unusual step reflecting the deep anger within Angela Merkel's government at the discovery of two suspected US spies within a week.
The scandal has plunged ties between Germany and one of its closest allies to a new low following last year's revelations from former US intelligence contractor Edward Snowden about widespread surveillance of Germans, including Merkel.
"The request was made in light of the ongoing investigation by the chief federal prosecutor and questions that have been raised for months about the activities of US intelligence services in Germany," Merkel's spokesman Steffen Seibert said.
On Wednesday, Berlin said it had discovered a suspected US spy in the defense ministry. That came just days after a German foreign intelligence worker was arrested on suspicion of being a CIA informant and admitted passing documents to a US contact.
Merkel delivered her strongest words yet on the alleged espionage, which she said belonged to the era of the Cold War.
"From my point of view, spying on allies ... is a waste of energy. We have so many problems, we should focus on the important things," the chancellor told reporters.
"In the Cold War maybe there was general mistrust. Today we are living in the 21st century. Today there are completely new threats," she said.
Merkel has come under pressure to take action against the United States, given public anger about the spying allegations.
Germans value their privacy highly due to memories of pervasive snooping by the Communist East German Stasi as well as the Nazis' Gestapo.
Seibert said the government took the events very seriously. It was essential for Germany to work with its Western partners, especially the United States, but that required "mutual trust and openness", he added.
Interior Minister Thomas de Maiziere said the information that the United States appeared to have obtained was "laughable", contrasting that with the "disproportionate and serious political damage" that the scandal had caused.