Correction: The headline in the print edition incorrectly identified Angela Merkel as the president of Germany. She is the chancellor.
BERLIN — Furious German officials said Wednesday that U.S. intelligence agencies may have been monitoring German Chancellor Angela Merkel’s cellphone, creating a fresh diplomatic headache for President Obama after a week in which other close allies condemned his administration over allegations of other spying misdeeds.
The German leader called Obama on Wednesday about the issue, forcing him to assure a European leader for the second time this week that the United States had not overstepped boundaries in its eavesdropping programs.
Obama told Merkel, an ally who has been upset since the extent of the U.S. surveillance programs was disclosed several months ago, that the United States is not eavesdropping on her telephone calls, the White House said Wednesday. Reports in Germany raised fears that such spying was taking place.
On Monday, Obama placed a phone call to France’s president, François Hollande, amid furor there over reports that millions of French phone calls had been recorded over a 30-day period last year. A top U.S. intelligence official denied those wiretapping reports Wednesday.
The accusations in Germany were prompted by reporting by the news magazine Der Spiegel, which has run many stories based on classified U.S. National Security Agency documents leaked by former NSA contractor Edward Snowden.
Der Spiegel said on its Web site Wednesday that the German intelligence agencies had, after a review of the magazine’s technical data, deemed its information on the monitoring of Merkel’s cellphone “over years” plausible enough to confront the U.S. government about it.
Merkel told Obama that if the accusations are confirmed, she “unequivocally disapproves of such practices and sees them as completely unacceptable,” her spokesman, Steffen Seibert, said in a statement, adding that any monitoring “would be a grave breach of trust.”
White House press secretary Jay Carney told reporters that Obama assured Merkel that the United States “is not monitoring and will not monitor” her phone conversations. Asked whether the statement left open the possibility that the NSA has tracked Merkel’s calls in the past, Carney said he did not have an answer to that question.
Obama visited Germany in June and met with Merkel, who expressed displeasure that the NSA had been monitoring the communications of German citizens. The new disclosures revived tensions that the White House had hoped had been resolved.
Merkel is a famously avid user of text messaging, and she is frequently photographed checking her smartphone during long sessions of Parliament and on the road. Earlier this year, she posed at a technology fair with a secure version of a Blackberry Z10; on the back of the phone was a decal of a black eagle, which is the emblem of modern Germany.
Swift condemnation of the United States came from across the political spectrum in Germany, where the news broke late Wednesday.
Revelations of NSA spying in Germany has caused major political uproar in the country this year, with investigations and fallout lasting long after outrage over Snowden’s revelations had settled in the United States. This month, Deutsche Telekom, Germany’s largest Internet and telephone provider, proposed routing important domestic e-mail traffic exclusively within German networks to ensure that it is secure from U.S. intelligence agencies.
Local news media also have reported that a domestically modified, highly secure version of the Blackberry Z10 has been selling out in the months since the NSA revelations were first published, driven by high demand from German government agencies.
The latest disclosure is likely to exacerbate anger in Europe over allegations that the NSA scooped up 70 million phone records of French citizens in one month, tapped the European Union’s offices in Washington and New York, and monitored phone lines at the E.U. headquarters in Brussels.
European lawmakers in Brussels have devoted themselves to the issue in recent weeks, taking up reams of legislation to improve data controls and take symbolic steps to suspend a pact with the U.S. to exchange financial data for counterterrorism purposes. They have also threatened to end negotiations over a trans-Atlantic free-trade pact, a key U.S. trade goal.
One E.U. lawmaker said the fresh accusations about the monitoring of Merkel’s cellphone would tip any lingering resistance to taking stronger action against the United States.
“Even the ‘hawks’ will feel eavesdropping on Angela Merkel is a bridge too far,” said Sophie in ’t Veld, a Liberal Democrat member of the European Parliament from the Netherlands, who said NSA Director Keith B. Alexander ought to appear before the body to respond to the broader allegations about U.S. spying.
“Public opinion in Europe is extremely negative about U.S. snooping,” she said. “People feel, ‘Is there no limit? Do we have no privacy anywhere?’ ”
Analysts say that European leaders privately recognize that some of the outrage rings hollow, given that their countries spy on the United States and on one another. But that argument does not assuage their audience, said James A. Lewis, a senior fellow at the Center for Strategic and International Studies in Washington.
“They say it’s a political issue and that the United States is going to have to come up with a fix that will improve transparency for American and European citizens,” Lewis said.
Nakashima reported from Washington. Scott Wilson in Washington contributed to this report.