The Germans "take this very seriously," Heisbourg said. "It could lead to a drifting away" from the United Sates.
German dismay was clear recently when Berlin broke with Washington and joined Brazil on a proposed United Nations resolution calling for an expansion of privacy rights on the Internet, diplomats say. Though the resolution is nonbinding, it would be a rebuke to U.S. spying practices and build pressure on Washington to rein in its foreign surveillance.
Brazil's president, Dilma Rousseff, canceled a long-planned visit to Washington in September to protest reported NSA spying on her phone. She subsequently told the U.N. General Assembly that American eavesdropping constitutes "a breach of international law" and a threat to democracy throughout the world.
A former administration diplomat, who asked to remain anonymous because of diplomatic sensitivities, said the U.N. was "exactly the kind of forum where the United States would not like this kind of issue to be adjudicated," because of a tradition of "America-bashing."
U.S. officials say privately that they believe they can manage the issue without serious damage to relations. But, in a shift, they have been signaling this week that they intend to set new, if narrow, limits on spying on national leaders.
German and EU delegations visited the White House on Wednesday to discuss the spying issue, meeting national security advisor Susan Rice, National Intelligence Director James R. Clapper and deputy national security advisor Lisa Monaco, among others, a spokeswoman said.
Officials on both sides are signaling they want an agreement to limit spying, allowing the Europeans to relieve public pressure for retaliation against the United States.
"The pressure will only grow for action unless the Europeans can say at home, 'We've changed the dynamic of the relationship,'" said Heather Conley, a Europe specialist at the Center for Strategic and International Studies in Washington.