The Obama administration is facing a breakdown in confidence from key allies over secret surveillance programs that reportedly installed the covert listening devices in EU offices.
Germany's move was its most direct expression of anger yet, and signaled that one of Washington's closest allies was unlikely to let the matter drop without at least a strong show of outrage.
"Eavesdropping on friends is unacceptable," German government spokesman Steffen Seibert told reporters in Berlin. "We're not in the Cold War anymore."
Germany has been among the European countries most anxious to reach a trade deal with the US, and it will likely try to strike a careful balance in its criticism of Washington.
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Europe's outage was triggered by a Sunday report by German news weekly Der Spiegel that the US National Security Agency bugged diplomats from friendly nations such as the EU offices in Washington, New York and Brussels. The report was partly based on an ongoing series of revelations of US eavesdropping leaked by former NSA contractor Edward Snowden.
It's unclear how widespread similar practices actually are. But some in Europe have raised concerns that US efforts include economic espionage against its allies.
In Berlin, Seibert said German officials told their US counterparts over the weekend they were "alienated" by the reported bugging, and would seek details from the Obama administration.
"Trust needs to be restored over this issue," especially in view of the trade negotiations just formally launched between the US and the 28-nation EU, Seibert said.