allegations that the United States has engaged in widespread eavesdropping on European internet users as well as spying on the EU.
Cecilia Malmstrom, the EU's home affairs commissioner, wrote to two senior US officials on Thursday to voice European concerns over implementation of the two agreements, both struck in the wake of the Sept. 11, 2001 attacks 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 said.
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 (TFTP) 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 United States too much access to European data, called on Thursday 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 United States 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.
Separately, German interior minister Hans-Peter Friedrich said the country's intelligence services were not spying on the United States and that he did not think German policymakers were under US surveillance.
"Anything else would be inacceptable," he was quoted by the mass-circulation Bild newspaper as saying.
"It would be inacceptable for Nato partners and friends to spy on German government offices and if that were the case, we would not only demand that this stops immediately, we would also demand an apology."