Following Mexico and France, Germany, another decades-long ally of Washington, has reportedly also fallen victim to the alleged US spying program.

It is shocking that millions of people, from rank-and-file citizens in France to German top leader Angela Merkel, may all have been under omnipresent US surveillance.

What's more, what happened in Germany and France may be only the tip of the iceberg.

A growing list of nations, developed or underdeveloped, Latin American or European, allies or rivals, have apparently been indiscriminately targeted by a massive USmonitoring network.

When classified files were leaked by former National Security Agency contractor Edward Snowden, US President Barack Obama asserted it was part of an effort to fight terrorism and protect the security of citizens.

But the latest revelations about US spying on the personal cellphones and email inboxes of heads of other countries have obviously contradicted and overthrown his argument.

Mutual trust will fade if such insensible policies are not adjusted, even with once-close friends.

Loss of faith in each other, the very centerpiece of political relations, will surely give nations pause for thought on their future collaboration with Washington.

As more and more countries voice anger over its spying program, the United States can only regain the trust of its partners and the world at large by offering honest explanations and increasing transparency about its surveillance.

This is especially true if it hopes to keep an untainted global image and continue its global leadership.