A decade-old plan to establish a foreign trade zone at Dulles International Airport appears finally to be rolling ahead.

The Washington Dulles Task Force, a private agency that promotes the airport, is close to forming a corporate body to apply for a federal permit for a zone. United Air Warehousing Associates, a Bethesda-based partnership, agreed last May to operate the zone inside a 33,000-square-foot warehouse it owns at Dulles.

Proponents express cautious hope that a zone will help draw new traffic to the underused airport, provide employment and spur industrial development in Fairfax and Loudoun counties by offering a new service to companies there.

"It's just one of the many elements in this puzzle that we're trying to put together that will assist in making Dulles airport a viable international port of entry," said Jack Herrity, chairman of the Fairfax County Board of Supervisors.

Foreign trade zones shelter importers from customs duties. Goods brought in from overseas may be stored, processed or re-exported without payment of tariffs required on the outside.

Tariffs are levied only if the goods leave the zone for the U.S. market. The Commerce Department has so far licensed more than 80 zones in the United States, but many have been plagued by losses and lack of business.

Robert Schott, a Dulles customs agent who will manage the Dulles zone if it is approved, said importers might bring in products such as electronic components to be assembled or repackaged. Duties paid when they left the zone would be lower than if they had entered the United States directly.

Schott also said companies that deal in surplus foreign weapons that U.S. gun-control laws bar from direct import had expressed interest in using the zone. There the weapons could be stored or modified to forms that meet U.S. laws, he said.

The zone might provide direct employment for a few local citizens, Schott said. But its main impact on employment would be to encourage international firms to come in and set up larger factories outside the Dulles zone.

The zone would begin in part of the 3,000 square feet of Dulles' Warehouse Three that Schott leases for his agent business. If zone business prospered, the owner, United Air Warehousing, would clear more space in the building, which is now occupied by tenants including British Airways, for zone activities.

He said that by starting small and continuing other business at the same time, the zone would have a better chance of avoiding the financial losses that have troubled other zones.