(c) 2013, Bloomberg News.

(c) 2013, Bloomberg News.

The following editorial appears on Bloomberg View:

Outrage over U.S. wiretapping of Angela Merkel's mobile phone has inspired two proposals worth considering. One is that the United States should quit spying on allied leaders. The second, floated by the German chancellor herself, is to add her country to the no-mutual-spying, intelligence sharing pact that the U.S. has had with its closest Anglophone allies since 1946.

Both of these ideas have the virtue of going beyond the inadequate response, "Everybody spies." Neither of them, however, would be as easy to carry out as they might sound.

Consider, first, Sen. Dianne Feinstein's proposal that the U.S. simply stop spying on friends. This, she suggests, could be accomplished as part of a full review of U.S. intelligence gathering. Such a review would be welcome, to assure the American public, as well as U.S. allies, that reasonable rules govern the National Security Agency.

The trouble is, new rules can limit the NSA only so much. Other countries couldn't be expected to follow suit if the U.S. makes such a commitment, and at some point the U.S. would find itself overwhelmingly tempted to break the promise. It's hard to imagine, for example, that any U.S. administration could have passed up the opportunity to listen in on phone conversations in 2003 between then German Chancellor Gerhard Schroeder and Russian President Vladimir Putin, as they looked for ways to thwart the U.S. invasion of Iraq.

And, of course, a breached U.S. promise, if made public, would create the same diplomatic blowback it was designed to eliminate.

What the NSA mainly needs is a mechanism to ensure that phone-tapping is done only when national security demands. What former NSA contractor Edward Snowden has exposed appears to have been the routine tapping 35 foreign leaders' telephones. Whatever decision was made to institute such a practice clearly didn't weigh the benefits against the potential costs if the taps were to be discovered.

Merkel's suggestion that Germany be part of a no-spying pact with the U.S. is also complicated. The multiple pacts that make up the so-called Five Eyes agreement among the U.S., Britain, Australia, Canada and New Zealand are rooted in the World War II collaboration between U.S. and British code breakers. Back then, the two countries essentially swapped assets: Britain got the technology that enabled it to listen in on the Japanese, while the U.S. got Britain's key to the German Enigma code. In 1946, they agreed to continue their collaboration against the Russians.

So why not create "Six Eyes," adding Germany to the group? Doing so would protect Merkel from further NSA snooping. It would also make more of Germany's intelligence resources available to the U.S., and vice versa. And it would catch up with history: Germany was the enemy when the pact was created, but is now a U.S. ally.

The complication is that Germany's foreign policy priorities don't align as closely with those of the U.S. as do Britain's. Germany engages more with Russia and China, for one thing, because those countries are mainstays of the export machine that powers half the German economy. Until recently, Germany also took a notably softer line than the U.S. on Iran. Germany's foreign ministry might ultimately balk at the pressures to align with the U.S. that an intelligence deal would create.

And though intelligence allies don't always have to agree on policy the U.S. and Britain split over the Suez Crisis and the Vietnam War when they do fall out, intelligence cooperation can be threatened without a very strong foundation to support it. Over the past half-century, the U.S. and Britain have built up significant shared interests, for instance, a U.S.-designed missile system that the British use as a nuclear deterrent and U.S. listening posts on U.K. property in Cyprus. The U.S. and German intelligence agencies lack such deep connections.

If an immediate expansion of the Five Eyes club is too ambitious, the U.S. might still work to integrate Germany more closely into its intelligence network. It would garner trust, a feeling that is now in short supply. And as the threats facing the U.S. become more complex, the U.S. will need more close friends.