Germany expressed shock Monday over reports of US spying on European institutions and said it had told Washington that it must restore trust in the wake of the damaging allegations.
"Europe and the United States are partners, are friends, are allies. Trust must be the basis of our cooperation and trust must be restored in this area," government spokesman Steffen Seibert told reporters.
"This is not the Cold War anymore."
Seibert said the government had learnt of the report in German news weekly Der Spiegel "with astonishment, better said with great displeasure, which was conveyed to the White House at the weekend".
"As a basic point, reports are not automatically facts and so we need to get to the bottom of this," he said.
"But if it is true that EU institutions and individual EU countries were spied on then we must say that bugging friends is unacceptable," he said.
"The government aims to ensure that we get to the bottom of this and if necessary there will be a unanimous and very clear reaction from Europe."
Seibert said Germany was in close consultation on the matter with fellow EU heavyweight France.
Der Spiegel said its report, which detailed covert surveillance by the US National Security Agency (NSA) on EU diplomatic missions, was based on confidential documents, some of which it had been able to consult via fugitive US leaker Edward Snowden.