The National Security Agency is trying to retain strict barriers on the export of computer chips that contain coding devices because it does not have a practical way of cracking the codes.
Advances in technology have coding devices small enough to be placed on computer chips, allowing even desktop computers to code and decode material at a relatively small cost.
And there is a growing appetite for such equipment among many companies and government agencies in the United States and abroad.
Many American companies are eager to battle for foreign customers. But NSA is battling any relaxation of export bans.
The agency, which is responsible for intelligence gathering and the security of military and government computers, spreads a vast electronic net around the globe, eavesdropping on telephone, radio and computer data with the assistance of allied governments.
In events like the shooting down of Korean Airlines flight 007 and the discovery of West German sales of chemical warfare manufacturing equipment to Libya, American electronic intelligence-gathering provided crucial data for government officials.
So the agency, based at Fort Meade, is dismayed at advances in technology that have created chip-sized coding devices. In the past, such coding and decoding required more powerful, more expensive computers.
The codes involve translating a message into a string of numbers, which is then disguised by multiplying it by other numbers. The key to retrieving the message involves knowing the numbers by which the message was multiplied.
Banks routinely use coded messages to transfer money electronically around the world, and that use is not restricted by the National Security Agency or other government agencies. But many companies and government agencies would like to encode telephone conversations and data communications about sensitive matters.
While the security agency has no authority over how such technology is used in the United States -- where it is increasingly employed by corporations and government agencies -- American intelligence officials have said privately that the security agency is determined to prevent the export of equipment that would make its work more difficult.
Asked to comment on the agency's approach to exports of coding equipment, a spokeswoman said in a written response: "Licenses for this equipment are reviewed on a case-by-case basis to determine the effect export could have on national security."
That puts the government at odds with major American computer and software companies, which say the restrictions are a significant handicap in international markets.
They also argue that the restrictions are quickly becoming meaningless, because a number of companies in Britain, Japan and elsewhere are now selling such equipment.
"The agency is acting on ill-conceived good intentions," said Albert R. Belisle, chairman of the information systems security committee of the American Banking Association.
And Stephen D. Bryen, a former Pentagon export control official and president of Secured Communications Technologies Inc., a maker of computer security equipment, said, "This is cutting off your nose to spite your face."