BERLIN ― Germans used to joke that Chancellor Angela Merkel’s penchant for communicating via fleeting text messages effectively marked the end of traditional historiography. Well, at least American spy agencies seem to have kept full track of the behind-the-scenes communications ― in Berlin and beyond.

Regrettably, U.S. President Barack Obama and his administration have yet to comprehend the scale and severity of the damage caused to America’s credibility among its European allies. The problem is not that countries spy on each other (they all do). Rather, it is the extent of U.S. intelligence gathering and America’s attitude toward allies that is most damaging.

Previous transatlantic clashes over diverse issues such as climate change, the detainees at Guantanamo Bay, and the Iraq War exposed a breakdown of mutual understanding, sometimes stemming from sharp differences over how best to achieve certain common objectives. But the wiretapping crisis and other troubling revelations from the former American intelligence contractor Edward J. Snowden point to a deeper problem: a crisis of mutual distrust that risks becoming a serious transatlantic rift at a time when closer political, economic, and security cooperation between Europe and the United States is needed more than ever.

There is probably nothing more destructive to friendly relations among democratic states than behavior by an ally that causes the other side to lose face at home. After all, it was Merkel who tried to calm the waters after the NSA scandal first hit Europe this summer. That is why the alleged U.S. wiretapping of her cellphone is so damaging for her, both personally and politically.

As someone who served in Merkel’s government from 2009 to 2011, I must admit that I was rather careless in the use of mobile communication devices while in office. In principle, of course, one should always assume that foreign intelligence services attempt to listen in on other governments’ conversations. But it makes a big difference whether such activities are conducted by Russia or China, or by an ally that repeatedly emphasizes the importance of close transatlantic friendship and cooperation.

Obama’s personality makes matters more complicated. It is hard to recall any other U.S. president who has been so personally disconnected from other heads of state. Instead of immediately reaching out to a friendly country, he decided to lie low and send White House Press Secretary Jay Carney to issue a rather awkward statement that the U.S. government “is not” and “will not” monitor Merkel’s communications. Of course, it does not take much interpretive skill to recognize a clumsy attempt to avoid confessing that U.S. intelligence services targeted Merkel in the past.

The Obama administration appears to have failed to ask itself some basic questions. How could it justify spying on a leader who is among America’s closest allies in NATO and in the Afghanistan mission ― a leader whom he invited to the Rose Garden to bestow the Presidential Medal of Freedom, the highest honor that America can give to a foreigner?

Moreover, Merkel was not the only target. In the case of France, how could the Obama administration justify targeting an ally that has tried hard to build trust with the U.S. by providing much-needed military and political cover in Libya and Syria? French President Franois Hollande, too, must feel like a fool ― not just as a result of U.S. surveillance, but also because he probably received no advance warning from his intelligence services about Obama’s sudden decision to ask Congress to pass a resolution prior to using military force in Syria.

Finally, how can Obama explain to the EU (whose delegation in Washington, DC, was also bugged) that it is crucially important to enter into honest, serious, and comprehensive negotiations to conclude a Transatlantic Trade and Investment Partnership? Prominent voices in Europe ― including the president of the European Parliament and the leader of Germany’s Social Democrats (who is about to form a coalition government with Merkel) ― are already demanding a suspension of the TTIP talks. The potential economic cost of a delay or a failure to achieve closer transatlantic economic integration could total hundreds of billions of dollars ― in addition to the incalculable damage done to America’s credibility in Europe.

There is much talk today about the risks of a new era of American isolationism and a lack of U.S. leadership in the world. It is important to remember that isolationism can be triggered not only by a potential retreat from global affairs, but also by the rather imprudent use of America’s hard and soft power on the world stage.

To escape the NSA mess, various options will be discussed. The new Franco-German push for an intelligence-sharing agreement with the U.S. is probably difficult to put into practice, especially considering that spy services operating around the world are not always fully controllable.

As a first step, Obama must rediscover the great communications skills that propelled him to the White House in the first place. From a public-diplomacy perspective, his handling of the surveillance scandal has been a complete failure. To contain the damage and begin to rebuild much-needed trust, Obama must issue a credible apology to Merkel, other Western allies, and their citizens.

In the American political context, issuing an apology, especially to foreign governments, is often viewed as a sign of weakness. In the case of the NSA scandal, an unequivocal apology by Obama is the only viable solution to leave the past behind and move forward. Unfortunately, the window of opportunity for such a gesture to be viewed in Europe as a much-awaited olive branch ― and a sign of real American strength and conviction ― is closing fast.

By Karl-Theodor zu Guttenberg

Karl-Theodor zu Guttenberg has served as Germany’s defense minister and minister of economics and technology. ― Ed.

(Project Syndicate)