The EU is threatening to suspend data sharing agreements with the US unless it shows it is respecting EU data privacy rules.
The threat reflects European disquiet about allegations that the US has engaged in widespread eavesdropping on European internet users as well as spying on the EU.
European Commissioner for Home Affairs Cecilia Malmstrom wrote to two senior US officials yesterday to voice European concerns over implementation of two agreements covering financial and travel data, both struck in the wake of 9/11 and regarded by Washington as important tools in the fight against terrorism.
"Should we fail to demonstrate the benefits of (the agreements) for our citizens and the fact that they have been implemented in full compliance with the law, their credibility will be seriously affected and in such a case I will be obliged to reconsider (whether) the conditions for their implementation are still met," Malmstrom wrote.
EU-US relations are going through a "delicate moment", she wrote in the letter to US Homeland Security Secretary Janet Napolitano and David Cohen, Treasury under-secretary for terrorism and financial intelligence.
"Mutual trust and confidence have been seriously eroded and I expect the US to do all that it can to restore them," she said in the letter, seen by Reuters.
Malmstrom is dispatching a team of officials to Washington next week for previously scheduled reviews of both information-sharing agreements.
The Terrorist Finance Tracking Programme provides the US Treasury with data stored in Europe on international financial transfers. The Passenger Name Record agreement covers data provided by passengers when booking tickets and checking in for flights. All such information is passed to the US Department of Homeland Security.
The United States and the EU need to show that the two data-sharing agreements "continue to bring benefits to our security and that the robust safeguards attached to them are respected to the full. We need complete transparency and a maximum of information on both programmes," Malmstrom wrote.
The European Parliament, some of whose members have long worried that the agreements granted the US too much access to European data, called yesterday for the scrapping of both accords unless Washington revealed the extent of its electronic spying operations in Europe.
Many of the eavesdropping reports were based on leaks by fugitive former US spy agency contractor Edward Snowden.
Last month, US officials confirmed the existence of an electronic spying operation codenamed PRISM, which according to Snowden collects data from European and other users of Google, Facebook, Skype and other US companies.
In a separate leak, the United States was accused of eavesdropping on EU offices and officials. France initially urged the EU to delay talks on an ambitious trade pact with the US over the alleged spying.
European Commission President Jose Manuel Barroso said later that Europe would begin the trade talks on Monday as planned but would at the same time set up EU-US working groups to examine the scope of US intelligence-gathering.