Hundreds of U.S. employes who work in some of the 10 other cities besides Washington with heavy federal employment could lose their jobs or be forced to move elsewhere if the Reagan administration firms up its plan to consolidate regional activities.

Most agencies now have complete headquarters-type operations in the 10 subcapitals that were set up by the Nixon administration to decentralize government. The cities are New York, Boston, Philadelphia, Atlanta, Dallas-Fort Worth, Kansas City, Chicago, Denver, Seattle and San Francisco.

But over the past decade federal employment in those subcapitals has grown, and they now employ a total of several hundred-thousand workers. Budget cutters contend that, as a result, there is too much duplication of effort in most of the cities.

Potential hit lists of cities that might be eliminated from the regional network have circulated for months. But there has been intense pressure from Senate and House members representing those states to keep the current employment system intact. Congress could conceivably block it with specific legislation, but there has been no move in that direction so far.

The politicians worry not only that services will be cut, but that their districts will lose out on federal jobs that, outside of Washington, are averaging $25,000 a year in pay.

Insiders say that the four cities most likely to be cut out of the regional network are Seattle, Denver, Kansas City and Boston. Their functions would be transferred to San Francisco, Chicago and New York.

"There is no 'final list' of cities to be eliminated from the network," an administration official said yesterday. "But we are looking at the possibility of consolidation and cost cutting, especially by eliminating duplicative functions in all of the cities.

"It makes no sense for 14 different agencies to have 14 personnel offices, 14 mail rooms, 14 administrative offices and so on," he said. " . . . Whatever we do" will make "some members of Congress unhappy," he added. " . . . But we do plan to do something and to begin the changes fairly soon."