Euro MPs have expressed concern at the way the US is gathering information from EU citizens that may be used in identifying terrorism suspects.
The EU has sought assurances over who can access passenger data
The EU justice commissioner told MEPs that banks in several EU countries were unaware details of transactions were going to the US treasury.
Franco Frattini also said negotiations over a new EU-US deal on air passenger data would be "a real challenge".
The US has had access to data about European air passengers since 2004.
The BBC's Alix Kroeger in Brussels says MEPs are uneasy about the kind of personal data being transmitted to the US authorities and the uses to which the information is put.
An interim deal allowing the US to access information on trans-Atlantic air passengers expires in July. The EU has until February to decide a strategy and timeline for the negotiations.
"The right to privacy for me is non-negotiable. It has to be respected," Mr Frattini said.
Washington says access to international bank transactions and passenger records is key to its fight against terrorism.
Last year, it emerged that a private company, Swift, which handles up to 11 million money transfers a year, had been passing information to the US authorities in violation of EU privacy rules - a finding Swift disputes.
BANK DATA CONTROVERSY
A Belgian money transfer firm, Swift handles 11m transactions per year
US agencies subpoenaed Swift to provide transaction data to help disrupt terrorist financing
The company has more than 7,500 clients, most of them global financial institutions
In November, the European Commission told Swift to stop violating EU privacy laws
Now MEPs want to know whether that data was fed into the US Automated Targeting System (ATS), which profiles possible terrorism suspects.
The US Department of Homeland Security (DHS) released information about the targeting system in December, explaining that it was intended to detect high-risk individuals not previously known to the law-enforcement community.
It gives anyone entering the US a numeric score, a measure of the risk he or she is thought to present, which the DHS said could be shared with state and local police and foreign governments.
"The European Parliament is fully supportive of proper co-operation across the Atlantic in fighting terrorism... What we don't accept is that there should be misuse of data," Liberal MEP Baroness Sarah Ludford told BBC World Service radio's World Today programme.
She said that ATS went "way beyond anything we had been led to understand the information would be used for".
MEPs also want to know whether the European Commission knows of any other requests to companies such as telecoms providers or insurers to make their data available to the Americans.
The commission has already written to the US government to ask whether the ATS profiling system is using air passenger records in ways that fall outside the current EU-US agreement.
One MEP, Dutch Liberal Sophie in't Veld, said it was not a question of being anti-American - American privacy laws were in fact tougher than those in the EU.
The problem was, she said, that those laws did not apply in Europe, and that there was no democratic debate on the American measures in either national parliaments or at the European level.