White House says more intelligence constraints needed
The White House has acknowledged the need for additional "constraints" on US intelligence gathering, amid claims of eavesdropping on allies.
Spokesman Jay Carney said an ongoing White House intelligence policy review would account for "privacy concerns".
Spain is the latest of several countries reported to have been the target of US collection of phone data.
A top Democrat in the Senate has said its intelligence panel will undertake a "major review" of US spying programmes.
Senator Dianne Feinstein said she was "totally opposed" to the National Security Agency's (NSA) intelligence gathering on leaders of US allies.
An EU delegate in Washington described the row as "a breakdown of trust".
On Monday Mr Carney, US President Barack Obama's spokesman, told reporters the administration "recognise[s] there needs to be additional constraints on how we gather and use intelligence".
He said the US did not use its intelligence gathering capabilities for the purpose of promoting its economic interests, and that Mr Obama was committed to ensuring "that we are collecting information not just because we can, but because we should, because we need it for our security".
"We also need to ensure that our intelligence resources are most effectively supporting our foreign policy and national security objectives, that we are more effectively weighing the risks and rewards of our activities," he said.
An across-the-board review of US intelligence resources, currently under way, is also expected to assist the administration in "properly accounting for both the security of our citizens and our allies and the privacy concerns shared by Americans and citizens around the world", Mr Carney added.
Mr Carney and Mr Obama have not commented on specific allegations that the US eavesdropped on international allies, including tapping the phones of foreign officials.
Earlier on Monday, representatives from the European Parliament's Committee on Civil Liberties, Justice and Home Affairs spoke to members of the US Congress about the alleged US spying on European leaders and citizens.
"We wanted to transmit to them first that this mass surveillance of EU citizens is a genuine concern," British Labour MEP Claude Moraes, a member of the delegation, told the BBC after the meetings.
But Mr Moraes said he and his fellow delegates were unsatisfied with the "stock" responses from US officials on the issue.
"They're giving us answers, but not the answers we want," he said. "We're getting a bit tired of this, 'Well, spying has always existed.'"
Spain has also urged the US to give details of any eavesdropping, amid reports the US National Security Agency (NSA) monitored 60 million Spanish telephone calls in a month.
The latest allegation, published by Spain's El Mundo newspaper, is that the NSA tracked tens of millions of phone calls, texts and emails of Spanish citizens, in December 2012 and January 2013. The monitoring allegedly peaked on 11 December.
Minister for European Affairs of Spain Inigo Mendez de Vigo called the allegations, if true, "inappropriate and unacceptable".
The allegations of US surveillance on international allies stemmed from documents leaked by fugitive ex-US intelligence contractor Edward Snowden, now living in Russia.
German Chancellor Angela Merkel is also sending intelligence officials to Washington to demand answers to claims that her phones were tapped.
German media reported that the US had bugged Ms Merkel's phone for more than a decade - and that the surveillance only ended a few months ago.
The German government hoped that trust between the two countries could be restored, a spokesman told a news conference in Berlin.
"It would be disturbing if these suspicions turned out to be true. But Germany and the United States can solve this problem together," Steffen Seibert said.
Senator Feinstein, the chair of the Senate intelligence panel, has previously expressed support for US intelligence programmes, but said in light of the Merkel revelations, her committee needed to know more.
"It is abundantly clear that a total review of all intelligence programmes is necessary so that members of the Senate Intelligence Committee are fully informed as to what is actually being carried out by the intelligence community," she said in a statement.
"It is my understanding that President Obama was not aware Chancellor Merkel's communications were being collected since 2002. That is a big problem," she said.
Meanwhile, a Japanese news agency reported the NSA asked the Japanese government in 2011 to help it monitor fibre-optic cables carrying personal data through Japan, to the Asia-Pacific region.
The reports, carried by Kyodo, say that this was intended to allow the US to spy on China, but that Japanese officials refused, citing legal restrictions and a shortage of personnel.