The United States and European Union nations have failed to bridge their differences over what Washington says is the need for armed guards on selected trans-Atlantic flights.

Many European civil aviation officials remain wary of the idea of using armed sky marshals on passenger aircraft. They told the American delegation that marshals would increase the risk to travelers. Some Scandinavian officials said, if there were a threat to a specific flight, they would prefer to cancel it, rather than allow armed guards aboard.

The meeting in Brussels followed Washington's demand last month for air marshals to be placed on certain flights by foreign airlines to the United States, if security officials determined that any such flight was at risk of a terrorist attack.

Britain and France, both of which had flights to the United States canceled or delayed over the recent Christmas and New Year holiday period, have expressed openness to the idea. But European Commission Spokesman Gilles Gantelet says most countries oppose the plan.

Mr. Gantelet says most countries are not in favor, and that some are actually firmly opposed to the idea. He says others might be able to look at certain situations on a case by case basis. But even they, he adds, feel the sky marshal proposal is not the only solution and, certainly, not a miracle solution.

The undersecretary at the U.S. Department of Homeland Security, Asa Hutchinson, says armed guards would not be obligatory on all flights to the United States, but would heighten security when intelligence shows that a specific flight may be threatened. After meeting with the European officials on Friday, Mr. Hutchinson told reporters the world has to handle the new terrorist threats with stronger security measures.

"We have moved into a new arena, where we have specific threat information that justifies an elevated security posture for particular flights of concern," he said. "And that is what we experienced last month. It is a new arena for those in aviation, and we need to develop the international standards to make sure we have the right response to those specific threats."

Mr. Hutchinson says foreign airliners, with or without sky marshals, can continue to fly to the United States. But he warns that, if U.S. authorities perceive that there is a credible threat to a specific flight, they reserve the right to bar the aircraft from U.S. airspace.