Updated

Some international airlines said Monday they would cooperate with a U.S. requirement for sky marshals on certain flights as part of a heightened terror alert. Others said they already were using armed marshals.

Britain has declared its willingness to deploy sky marshals. The Department of Transport said Britain was in "regular contact with the U.S. government about security matters," but stressed that "only the U.K. can authorize the placing of air marshals on U.K. carriers."

Britain's pilots' union opposes armed guards on flights, but British Airways (search) said it would accept air marshals if that would improve safety.

The Bush administration said Monday it will require international air carriers in certain cases to place armed law enforcement officers on cargo and passenger flights to, from and over the United States.

In Germany, Lufthansa (search) spokesman Thomas Jachnow said the airline had not been contacted by Washington about flight security, but that Lufthansa has been carrying sky marshals on some of its trans-Atlantic passenger flights since the Sept. 11 attacks by Al Qaeda (search).

KLM Royal Dutch Airlines said introducing armed marshals on trans-Atlantic flights was among several new security measures it was discussing with the Dutch government.

Peter Coyles, spokesman for Transport Canada, said certain Canadian flights to the United States, including all to Ronald Reagan Washington National Airport, had carried armed law enforcement officers since shortly after Sept. 11.

Air Canada said it was aware of the U.S. Homeland Security Department's request and was complying with it.

In Russia, Aeroflot spokeswoman Irina Dananberg said she wasn't aware such a request had been made to the airline, but it was ready to cooperate.

A spokeswoman for Air France said unarmed security agents had been aboard "flights judged to be sensitive" since the attacks on New York and Washington in 2001, but she had no comment on the U.S. directive. The airline canceled six flights between Paris and Los Angeles on Wednesday and Thursday following security talks between U.S. and French officials.

French Transport Ministry spokesman Olivier Mousson did not say whether France would conform to the request, but said, "The French and the Americans cooperate totally in the struggle against terrorism. We work hand-in-hand."

He also said U.S. security agents have inspected security at French airports since the United States raised its alert level.

Several other airlines -- including TAP Air Portugal, Austria's national carrier, Austrian, and South African Airways -- said they had not been contacted by U.S. authorities regarding deployment of sky marshals.

Italy's civil aviation agency said it had received no requests to place security personnel on flights from Italy. But Italian consumer group Codacons asked on Monday for armed police on international flights leaving Italy, beginning Jan. 5., in response to increased security concerns.

British Airways said it would accept armed officers on certain flights if it was "satisfied that safety was thereby enhanced" sufficiently for the service to proceed. "If BA was not fully satisfied, the flight would not take place," the carrier said in a statement.

Britain announced in December 2002 that it had the capability to use sky marshals and would deploy them "where and when" necessary.

On Sunday, the government said it had increased "security measures on the ground and in the air" for trans-Atlantic flights in response to the Code Orange alert in America and said sky marshals would be used "where appropriate."

Airline pilots, however, expressed concern. "We cannot agree with the government's decision to put armed guards on aircraft as we believe this will do more harm than good." said Jim McAuslan, general secretary of the British Airline Pilots Association. "We do not want guns on planes."

Britain's transport secretary, Alistair Darling, said pilots would be kept informed if a sky marshal was on board and said they were "one of the last lines of defense."

"Of course the best thing to do is to try to stop people getting on to the plane in the first place," he told British Broadcasting Corp. radio.