For all his concerns, Mr. Obama does not plan any extraordinary outreach to Ms. Merkel, an official said, noting that some in the administration also feel that Germany should not overreact to the case or conflate it with the privacy issues raised by the N.S.A.’s surveillance.

Some experts say the recent tensions betray a lack of attention in Washington to its relationship with Berlin. “Bush and especially Obama have treated it as a ‘solved problem’ requiring no further American involvement,” said John C. Kornblum, a former American ambassador to Germany. “Recent events have demonstrated that just the opposite is the case. Germany is still deeply conflicted about itself and about the world around it.”

The White House and the C.I.A. both declined to comment on the case, with a spokeswoman for the National Security Council, Caitlin M. Hayden, saying, “We’re certainly not going to discuss who knew what and when in regards to the allegations.”

On Tuesday, the chairwoman and the ranking member of the Senate Intelligence Committee said in separate interviews that Mr. Brennan had briefed them about the matter, but they refused to divulge any details of the conversations.

Senator Dianne Feinstein, the California Democrat who is chairwoman of the committee, expressed concern about the damage that could come to American-German relations. “We need to relook at this whole situation, how we handle our allies,” said Ms. Feinstein, who said she met with German Parliament members who she said were “very upset” by the reports.

The ranking Republican, Senator Saxby Chambliss of Georgia, sounded a note of caution about the allegations. “I’m not sure how much of it is true,” he said. “That’s going to dictate how serious it is.”

Over the past year, the German government has tried to use the Snowden revelations — chiefly the embarrassing disclosure about Ms. Merkel’s cellphone — as leverage to negotiate a non-spying pact between the United States and Germany. The United States has such arrangements with Australia, Britain, Canada and New Zealand.