The United States will push for more flexible arrangements with the European Union on how its agencies use the personal records of air passengers to combat terrorism.
The United States and EU this month agreed temporary rules giving US law enforcement agencies easier access to air passenger data as part of measures brought in after September 11th.
But the chief US negotiator of the pact, which is due to be replaced by a permanent accord after July 2007, said Washington would push for the right to hold data on passengers for longer than the current arrangement of three-and-a-half years.
"Our usual rule for law enforcement data is that it is kept for about 40 years, but the real question is how long is it likely to be relevant," said Stewart Baker, assistant secretary for policy at the Department of Homeland Security.
Mr Baker described restrictions included in the current accord as "almost a code of conduct for the United States" but said he was confident that negotiations would lead to some of them being relaxed in any future pact.
"I am quite hopeful we will be able to have a more flexible arrangement that reflects the fact that we have the same moderately competing goals - better security and good privacy as well," he told a news briefing in Brussels.
Under the October 6th deal, European airlines must pass on up to 34 items of data, including passengers' addresses, telephone numbers and credit card details, to be allowed to land at US airports.
Limits apply on the access to the data enjoyed by US agencies, how long they can keep the records and how they can use them.
EU ministers rubber-stamped the deal on Monday and US officials are expected to do the same later this week.