Travelers checking in to budget hotels near major airports might be surprised to find themselves standing next to undercover federal air marshals. They'll be the guests asking for "the air marshal's discount."

So much for working undercover.

Under a new policy, when air marshals travel away from their home bases -- as they do continually -- they will have to stay at a short list of selected hotels. They will also be required to identify themselves as air marshals to receive a special rate their agency has negotiated with the innkeepers -- below the regular government discount they now get.

That, as many air marshals see it, is the latest bureaucratic blow to their effort to maintain security and keep potential terrorists from identifying them.

The hotel policy "has caused great anxiety" as marshals "worry about the various security risks involved in having a set, observable and discernible pattern of activity regarding their hotel accommodations," a lawyer for the Federal Law Enforcement Officers Association wrote the Department of Homeland Security last month.

The dispute is the latest turn in an increasingly rancorous relationship between the marshals and their federal bosses. The marshals already were upset by rigid dress codes and grooming rules they say make them conspicuous among today's dressed-down air travelers.

The labor-management feud is surprising because, in the immediate aftermath of the Sept. 11, 2001, attacks, the air marshals received an enhanced role as front-line warriors in the battle against terrorism.

The issues of identifying themselves to hotel clerks and being required to stay together in a small number of hotels may not seem like a big deal, but in the present climate of heightened concern about terrorist attacks -- along with recent revelations about the extent of al Qaeda's surveillance operations in the United States -- marshals say the problem is significant.

"If terrorists . . . were to ascertain that a predetermined list of hotels was being used . . . these sites would be high value targets in and of themselves," lawyer Mark L. Cohen wrote in an Aug. 5 letter. The association represents officers from about 50 federal agencies, including about 1,300 air marshals.

A spokesman for the Federal Air Marshal Service defended the new policy, saying its chief aim is rapid access to marshals in an emergency. Budgetary savings would only be "a byproduct," said David M. Adams.

"This policy is designed for the safety of our personnel, and so that during enhanced emergencies we can recall the marshals quickly while they are on mission deployment," Adams said.

But several marshals said in interviews that the agency already has the ability to muster its troops at a moment's notice. Marshals are required to be available 24 hours a day, seven days a week, they said. And they usually stay in lodgings near the airport.

"They have more than enough ways to get hold of us," said a marshal based on the East Coast. "We all have government cell phones and we all have PDAs that do e-mail."

The marshal asked not to be identified, as did others interviewed, because they can be fired for talking to reporters without authorization.

Marshals have been circulating e-mails from supervisors in Miami and Orlando strongly implying that a push for cost savings was the central motivation for the changes.

"This has been done, in part, to try to realize a cost savings for the Service," said the Miami memo, which did not offer other rationale.

It's unclear how much the agency would save from its $600 million budget by using select hotels.

For supervisors to order marshals to identify themselves to get the special rate "is nuts," said a second marshal.

Marshals now arrange their own lodging. Like other federal employees, they can pick any hotel that offers a rate established by the General Services Administration for travel on government business. Federal employees are supposed to identify themselves to obtain the discount. But marshals said they usually manage to finesse things without giving away what the kind of jobs they do.

Some worry that preferred hotels could become targets for surveillance -- or, worse, for an attack. By staking out a handful of hotels in major cities, a foe could conceivably track the comings and goings of hundreds of marshals. "We are concerned that you could build a photo library of a scary percentage of air marshals," said Jon Adler, a vice president of the Federal Law Enforcement Agents Association.

Adams said marshals should immediately report any suspicious snooping at the preferred hotels. "If we determined there was any surveillance activity going on, we could change the hotels," he said.

That might be too late, said one marshal, noting the recent security alerts in New York and Washington were based partly on the discovery of al Qaeda surveillance that had gone undetected for several years.