BERLIN  - US President Barack Obama told Germans and their leader on Saturday he would not let intelligence work damage relations, and differences of opinion between the two countries was no reason to wiretap.

In a rare interview on German TV, Obama set out to mend ties frayed last year by media reports citing leaked intelligence documents that Washington was spying on European Union citizens and had bugged Chancellor Angela Merkel's mobile phone.

"I must and cannot damage this relationship through surveillance measures that obstruct our trusting communication," Obama told ZDF public TV, according to a German translation of his comments.

"As long as I am the President of the United States, the German Chancellor need not worry about that," he added.

The interview came a day after Obama banned US eavesdropping on the leaders of close allies, among a series of reforms triggered by the revelations of former US security contractor Edward Snowden.

Obama's comments on Saturday were his clearest indication that Germany was included in that list of allies.

Merkel and he "may not always be of the same opinion on issues of foreign policy, but that is no reason to wiretap," he told ZDF.

The German leader accused the United States of an unacceptable breach of trust after the allegations about her mobile in October and phoned Obama to tell him any bugging was unacceptable. Berlin has since been pushing for a sweeping "no-spy" agreement with Washington.

Obama stopped short of apologising over the allegations on Saturday and defended the importance of US intelligence work for international security.

The capabilities of the US services went "beyond the abilities of many other states," he said, and that meant a "special responsibility for the United States".

"Why would we need intelligence services if they only found out things you can read in Spiegel (magazine) or the New York Times," he asked.

"Per definition, those services are tasked with finding out what people are planning, what goes on in their minds, what their aims are. That supports our diplomatic and political goals."

Even as the White House put the final touches on its security reform plan this week, media outlets reported that the National Security Agency gathers nearly 200 million text messages a day from around the world and has put software in almost 100,000 computers allowing it to spy on those devices.

Snowden, living in asylum in Russia, is wanted on espionage charges, although some Americans would like him to be granted amnesty for exposing secrets they feel needed to be made public.