Asa Hutchinson, U.S. undersecretary for border and transportation security, sought to convince European civil aviation officials that armed guards are needed to thwart terrorist attacks in planes.
But although Britain and France were open to the idea, other Europeans largely stuck to their reservations.
"Use of weapons on board an aircraft is always potentially dangerous because there are some very sensitive electronics on board every aircraft," said Lars Lovkvist, Finnish Air Transport Authority Director.
"If there really is a grave serious threat, we would cancel individual flights and not use sky marshals," he said.
Hutchinson said the United States was not demanding air marshals on every flight — only on "selective flights on a case by case basis" — but he disagreed with Europeans that marshals were not needed.
Air marshals "give a higher level of security," he told reporters. "We have used it well in the United States, and the ultimate goal we are trying to accomplish is the safety of the passengers."
Hutchinson told reporters after the meeting that Washington would approach individual European nations to seek bilateral protocols on security measures for trans-Atlantic flights, including when and how air marshals would be used.
Separately, the European Union's head office drew up a list of items that passengers boarding in any of the 15 EU nations will be banned from taking onto planes. The list ranges from guns, explosives and machetes to ice skates, fishing rods and paint thinner.
Most of the articles are already banned individually by EU nations, but the European Commission said a standardized list for the whole bloc would improve safety and provide clarity for passengers.
It also adopted a list of goods banned baggage holds, including fireworks, bleach and radioactive material.
Following heightened security over the Christmas holidays, Washington is demanding stepped-up cooperation to counter hijackers. However, many in Europe fear the use of armed guards on commercial flights could put crew and passengers at risk.
After the Sept. 11 attacks, the United States expanded its force of air marshals, sharpshooters who are trained to stop hijackings. They wear civilian clothes and carry special bullets designed to kill without penetrating the metal skin of aircraft.
But many countries are still wary.
"We do not want weapons in the cabin," said Bo Eckerbert of the Swedish Aviation Administration. "It may even create more problems than it solves."
Airlines already have to supply U.S. authorities with more data on passengers on trans-Atlantic flights, but a December deal brokered between EU headquarters and Washington limited the use of such data to comply with EU privacy rules.
Finland's national carrier, Finnair, which flies to New York and other North American cities, is against the use of marshals, while package tour operator Thomas Cook, which operates charter flights between London and Orlando, Fla., also said it would not accept them.
Pilot organizations in Britain, Spain and other countries also expressed strong reservations.
The U.S. Department of Homeland Security announced Dec. 29 that airlines would be required to place armed law enforcement officers on flights to the United States "where necessary."
The announcement came after U.S. authorities raised their terrorism alert to orange, the second-highest level, and increased security surrounding international flights.
More than a dozen flights to the United States on British Airways, Aeromexico and Air France have been canceled or delayed since New Year's Eve because of security fears.