White House spokesman Josh Earnest said Washington was aware of the report that a German double agent had spied for the US, but said he could not comment on intelligence matters.
"We are committed to making sure that we resolve this issue with the Germans appropriately," Earnest said.
"This is an intelligence matter," Earnest said. "It's a matter that is under investigation by the German law enforcement authorities, so I'm not in a position to comment on it from here."
US-German relations were put to test last year by the revelation that the National Security Agency had been spying on the mobile phone of Chancellor Angela Merkel.
On Friday, the US ambassador to Berlin was called to a meeting at the Foreign Ministry over reports that a 31-year-old employee of the German foreign intelligence agency had been feeding information to a spy agency for two years.
Though Earnest would not confirm or deny the allegations, he sought to limit any diplomatic damage by stressing the importance of the "close partnership" between Germany and the US.
"The relationship that the US has with Germany is incredibly important," Earnest said. "That partnership is built on respect. It is based on decades of cooperation and shared values."
'Clear contradiction of mutual trust'
Merkel addressed the matter earlier on Monday, saying that "if the reports are correct, it would be a serious case."
"It would be for me a clear contradiction as to what I consider to be trusting cooperation between agencies and partners," she added.
Over the weekend, the newspaper Frankfurter Allgemeine Zeitung am Sonntag reported that the suspect, who was arrested last Wednesday, had also made contact with Russian authorities.
Government spokeswoman Christiane Wirtz said Germany was waiting until a prosecution report on the claims had been completed before giving a detailed response.
rc/mkg (AFP, Reuters, dpa)