The commission said the United States was making extra security demands on newer member nations in exchange for eventually allowing their citizens to travel without visas, like people in most of the EU's 27 states.

"A text I saw ... is unacceptable, is just way beyond anything that can be done," said Jonathan Faull, director general of the commission's security and justice department. "It is necessary that Washington realise that."

"We don't negotiate matters that are dealt with in Washington with the state of California," he told reporters. "That would be disrespectful and we expect the United States to be similarly respectful of our law and system."

He did not disclose exactly what demands were being made of the mainly ex-communist states that joined the EU in 2004 — but he did confirm that it might involve surrendering the data of people who fly over EU territory.

The EU and the United States struck a deal last June on the transfer of personal information about passengers flying from Europe to the United States for use in Washington's "war on terror".

The agreement provides the US Department of Homeland Security (DHS) with 19 categories of data about air travellers which the DHS could keep for 15 years and share with other law enforcement agencies under certain conditions.

The deal ended more than a year of transatlantic legal wrangling over information which could be taken from tens of thousands of passengers each day, a process that has raised deep privacy concerns in Europe.

Throughout those negotiations, the commission struggled to maintain EU unity and gain the upper hand, knowing full well the United States could decide to conclude bilateral accords with individual states.

"Some of the requirements in the so-called memorandum of understanding that I've seen ... go too far. They go beyond the PNR the union as a whole concluded with the United States last year," Faull said.

"Some of them are not matters to be discussed between individual member states and the United States, they're a matter for the European Union to discuss with the United States."

The commission has held off taking action against the United States even though Washington continues to refuse visa-free entry to some EU citizens, but Faull raised the prospect that some retaliation could be coming.

"We have not imposed a visa obligation on any category of US citizen but our patience can't last for ever," he said.

The so-called "visa waiver" programme obliges citizens from Greece and nine of the 10 countries that joined in 2004 — Slovenia is the exception — to have visas, even for a short stay, when they arrive on US territory.

US policy has been to assess each country individually, and to refuse visa-waiver status based on a number of criteria, like the number of visas which have been refused or security issues.

Faull said he would discuss the whole issue with EU nations "at a very high level" in the coming days in order to hammer out a common position that would then be shared with Washington.

AFP