The EU on Wednesday laid down steps Washington must take to restore trust after a huge spying scandal, including giving EU citizens the right to US legal redress to protect personal data.
"Massive spying on our citizens, companies and leaders is unacceptable," EU Justice Commissioner Viviane Reding said, adding there was "now a window of opportunity to rebuild trust which we expect our American partners to use."
An umbrella agreement being negotiated on EU-US data protection "has to give European citizens concrete and enforceable rights, notably the right to judicial redress in the US whenever their personal data are being processed in the US," Reding said in a statement.
A key concern in Europe -- where memories of surveillance by fascist and communist dictatorships remain alive -- is the pressure Washington exerts on giant US companies to hand over personal data, including of EU citizens, on national security grounds.
Up to now Brussels and Washington have reconciled their differences in a 'Safe Harbour' agreement which aims to ensure US companies respect EU norms on commercial personal data use.
In the EU, personal data protection is considered a basic right whose commercial use must be carefully controlled.
Safe Harbour now needs to be tightened up, Reding said, with 13 suggested changes, including a provision requiring US companies to make clear the extent to which US authorities have the right to collect and process data they may have gathered.
The national security justification often cited for such government access must also be used only if strictly necessary.
Reding said the EU must conclude reform of its own data protection laws and be actively involved to ensure that US reforms promised by President Barack Obama "also benefit EU citizens."
Highlighted by the reported US tapping of German Chancellor Angela Merkel's mobile phone, data protection has become a hugely sensitive topic since intelligence leaker Edward Snowden described a massive network of US spy operations on friend and foe alike earlier this year.
The uproar prompted the European Parliament to call for talks on a massive free trade deal with the United States to be halted and the Safe Harbour system to be scrapped in protest.
But the European Commission stressed again Wednesday that data protection standards would not be part of the negotiations on the planned Transatlantic Trade and Investment Partnership.