Updated

European Union officials head into complex security talks in Washington on Monday threatening to suspend key data-swapping deals with the United States amid continuing anger over reports of US snooping.

Brussels this week warned Washington in a letter obtained by AFP that it was ready "to reconsider" two key anti-terrorist data-sharing deals failing US assurances of their "full compliance with the law".

The warning over hard-won agreements to share airline passenger data and SWIFT banking details as part of the global fight against terrorism comes amid public outrage over reports that US agencies spied on Europeans as well as on their institutions and embassies.

"We are experiencing a delicate moment in our relations with the US," the EU's Home Affairs Commissioner Cecilia Malmstroem said in a letter to Homeland Security Secretary Janet Napolitano.

"Mutual trust and confidence have been seriously eroded and I expect the US to do all that it can to restore them."

Malmstroem said her staff would be in Washington next week for the first review of the 2012 Passenger Name Record (PNR) agreement -- enabling the transfer of EU air passenger data to US authorities -- as well as a review of the older Terrorist Financing Tracking Program (TFTP), which accesses the SWIFT global interbank transfer network.

"Should we fail to demonstrate the benefits of the TFTP and PNR instruments 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 if the conditions for their implementation are still met."

The review talks will be one of three key EU-US meetings taking place in Washington next week as the dispute over snooping allegations rumbles on.

Amid the fallout in the row France called for the suspension of anxiously-awaited negotiations on a mega EU-US trade deal that kick off in Washington on Monday.

But a delay to what is being described as history's biggest trade deal was opposed by Germany and so the US then offered in compromise to hold talks in parallel on security issues to assuage concerns.

Speaking in the Lithuanian capital Friday, European Commission president Jose Manuel Barroso officially confirmed that EU-US security talks would begin alongside the trade negotiations.

The meeting "will look for clarification on issues like data protection and privacy rights," he said at a news conference in Vilnius.

Barroso confirmed however that the EU team would not discuss intelligence matters with US experts, in line with insistence notably from Britain that intelligence was not the remit of the bloc.

Should intelligence matters come up they "will be discussed by member states with the United Tates because this is national competence," Barroso said.

Britain had objected to a US offer to hold talks with the 28-nation bloc both on intelligence gathering and on data privacy and oversight.

Ties between Washington and Brussels have been strained since Edward Snowden, a former contractor with the National Security Agency (NSA), revealed that the US was systematically seizing vast amounts of Internet and telephone data around the world.

Reports in the Guardian and Der Spiegel in recent days then detailed widespread covert surveillance by the NSA of EU offices, including diplomatic missions in Washington and at the United Nations in New York, as well as at its Brussels headquarters.