US President Barack Obama on Monday said he would fully inform European allies angry over allegations Washington had bugged their offices, once he had all the facts.
"When we have an answer, we will make sure to provide all the information that our allies want," Obama said at a press conference in Tanzania.
The European Union, Paris and Berlin have demanded answers from Washington, following the latest spying claims attributed to fugitive leaker Edward Snowden.
The report in German weekly Der Spiegel detailed covert surveillance by the US National Security Agency (NSA) on EU diplomatic missions.
Obama said the United States will "take a look at this article and figure out what they may or not be talking about. What we will do is communicate with our allies appropriately."
Whilst stopping short of acknowledging any spying by the US, he suggested all parties systematically snoop on either other.
"In European capitals there are people who are interested, if not in what I had for breakfast, at least what my talking points would be if I am talking to their leaders," Obama said.
But he also underlined his close relations with European allies, adding that "if I want to know what Chancellor Merkel is thinking, I will call Chancellor (Angela) Merkel", and in the same manner, with French President Francois Hollande.
One document, dated September 2010 and classed as "strictly confidential", describes how the NSA kept tabs on the European Union's mission in Washington, Der Spiegel said.
Microphones were installed in the building and the computer network was infiltrated, giving the agency access to emails and internal documents.
The EU delegation at the United Nations was subject to similar surveillance, Der Spiegel said, adding that the spying also extended to the 28-member bloc's Brussels headquarters.
"Here's one thing (US and other intelligence services) are going to be doing, they are going to be trying to understand the world better, and what is going on in capitals around the world," he said, adding that "they are seeking additional insight beyond what is available from open sources."