The European Union's financial services chief on Tuesday said the EU was waiting for US government answers about its spying on allies, and suggested certain actions should stop.
Michel Barnier, EU commissioner for internal market and services, said the revelations of US snooping had shaken European confidence at a time when both sides are pursuing an ambitious free-trade agreement.
"This business of wiretapping and espionage casts a question mark over the mutual confidence of allies," Barnier said at a news conference in Washington.
"That requires that we speak more about it, not less, and that all the cards are put on the table," he said.
"That is why we have launched with member states... a high-level group to get to the bottom of things, to know the truth, obtain clear and precise responses about this question of spying, especially on our institutions and citizens."
Barnier declined to comment on whether the spying revelations would affect US-EU trade negotiations that started on July 8 in Washington.
The spy row, which erupted after leaks by former National Security Agency contractor Edward Snowden, cast a shadow over the launch of talks last week on the Transatlantic Trade and Investment Partnership (TTIP), aimed at creating the world's biggest free-trade bloc.
The spying has infuriated Europeans. France had pushed to have the trade talks delayed, but Europeans agreed they would go ahead as planned if simultaneous negotiations were held on the NSA actions.
European officials gathered at the US Department of Justice while the trade talks were held to discuss the super-secret NSA's activities.
"I hope the Americans have understood that, to attain all the conditions for the trust that we need for success -- notably with TTIP -- it is necessary that we really get the answers, and perhaps that a certain number of things cease," Barnier said.
The French official, a member of the European Commission, the EU executive body, also called for the 28-nation bloc to "adopt measures to protect its citizens' data," defending a proposal by German Chancellor Angela Merkel for regulation of private information.
"Europeans now have to stop being naive," Barnier said.
On Wednesday Barnier is set to wrap up a four-day visit in the US capital, which has included a meeting with US Treasury Secretary Jacob Lew.