Washington's typical response to revelations of electronic spying on the communications of its own people and foreigners alike has been aggressive defence, such as US lawmakers' recent claims that the National Security Agency's telephone surveillance programme has "saved thousands of lives" and that there is no need to apologise for it. That line has been harder to sustain since the latest of a series of revelations by former American intelligence contractor Edward Snowden, which has prompted calls for President Barack Obama to ban eavesdropping on the leaders of friendly nations.
The US has not denied that the NSA listened to the cellphone conversations of German chancellor Dr Angela Merkel for a decade - an allegation that has aroused deep anger and disquiet in Berlin and the European Union. She is, after all, not only the democratically elected leader of a close Western ally but a key figure in Europe. It is still not clear when President Barack Obama learned of the surveillance, just that it was he who ordered a halt to it.
All nations spy on each other, including close allies. Moscow and Beijing surely would not relish the prospect of exposure by a Russian or Chinese version of Snowden. The Merkel affair is a reminder that in the case of close friends, any real intelligence gains have to be weighed against the risk of damage to the essence of good relations - trust. It lends weight to concerns in America and abroad about the need for constraints on the NSA's surveillance activities.
It is time for debate about a proper balance between the right to privacy and safeguarding security and economic interests. A White House spokesman has said, rightly, that the US needs to make sure it is collecting intelligence for legitimate security needs and not "just because we can". Meanwhile, for the sake of the international fight against terrorism, Washington urgently needs to mend diplomatic fences damaged by the Snowden revelations.