On Sunday evening a senior administration official said of the spying on allies that the White House believed that “it’s not that the N.S.A. or the intelligence community were going rogue or operating out of bounds.” But the official added that two reviews of N.S.A. practices ordered by Mr. Obama are “to ensure that the intelligence community is getting the appropriate guidance from policy makers.”

The Obama administration has said as little as possible about the reports of the operation against Ms. Merkel, seemingly in hopes it will blow over. But the recent disclosures appear to have raised many new questions, including several that White House officials, saying they could not discuss classified intelligence matters, have been trying to deflect.

First among them is why Mr. Obama, by White House and N.S.A. accounts, was not made aware of the surveillance of a close ally. American officials have said that while the president approves major operations for the intelligence agencies, he does not get involved in the selection of targets. “I think this just wasn’t on the White House radar,” said one administration official familiar with internal discussions of the subject.

But given the delicacy of the subject — and previous German protests about other forms of surveillance — it is unclear why General Alexander or James R. Clapper Jr., the director of national intelligence, would not have informed Mr. Obama as soon as the phone taps were disclosed. The White House has never said when any operations against Ms. Merkel ended, but the database entry published by Der Spiegel appeared to be current earlier this year. The Wall Street Journal reported late on Sunday that the N.S.A. program that was used to spy on a number of world leaders ended over the summer.

Even if Mr. Obama was unaware, it is possible some of his senior staff were. While the President’s Daily Brief, the intelligence assessment of global threats Mr. Obama is given each day, is heavy on analysis, some of his aides receive far more detailed accounts of intercepts in their daily binders of intelligence assessments.

In the United States, Representative Mike Rogers, a Michigan Republican, vigorously defended American surveillance activities in Europe, saying that much of the anger over them flowed from a misunderstanding of their scope and intent.

Mr. Rogers insisted on the CNN program “State of the Union” that the N.S.A. surveillance program, particularly regarding France, but also Germany, had been badly misrepresented and that it was designed to protect them and other countries from the threat of terrorist attacks.