Spying claims: EU meets US security officials
28 October 2013 Last updated at 17:27 GMT
Spain has urged the US to give details of any eavesdropping, amid reports it monitored 60 million Spanish telephone calls in a month.
An EU delegation is meeting officials in Washington to convey their concerns, calling the alleged spying "a breakdown of trust".
British Labour MEP Claude Moraes, head of the European delegation, said his colleagues had told US officials the allegations were of "genuine concern".