The White House would not deny that the United States snooped on German Chancellor Angela Merkel's cellphone communications in the past and acknowledged on Thursday that allegations of U.S. spying have created tensions with allies.
"We are not going to comment publicly on every specified alleged intelligence activity," White House spokesman Jay Carney said. "The president spoke with Chancellor Merkel, reassured her that the United States is not and will not monitor the chancellor's communications."
Merkel has reacted indignantly to information gathered by the German government that the United States may have monitored conversations from her official cellphone. She demanded clarification from Obama in a telephone conversation on Wednesday, telling him if such surveillance had taken place, it would represent a grave breach of trust.
Pressed on the issue at a news briefing, Carney repeated that the United States reserves the right to conduct surveillance and said Obama has initiated a review of intelligence gathering to balance security needs with legitimate privacy rights.
As part of the fallout from classified information made public by former National Security Agency contractor Edward Snowden, revelations the United States has listened in on the communications of world leaders have ruffled feathers in France, Brazil, and Mexico.
The White House spokesman conceded that those allegations have hurt ties with countries the United States is close to.
"This is a clear source of tension in some of our relationships," Carney said.
Germany's foreign minister summoned the United States' ambassador, John B. Emerson, to discuss the issue, a German government spokesman said on Thursday.
Obama is aware that spying on conversations is an especially sensitive topic in Germany, where many citizens were monitored by state authorities in East Germany before German unification, Carney said.