Japan's Isuzu Motors Ltd. "is seriously considering the possibility" of establishing a low-volume, light-truck assembly facility in the Mid-Atlantic region, perhaps in the Baltimore area, Isuzu officials said yesterday.

The facility would operate under the aegis of Isuzu Truck of America Inc., the commercial truck distribution division of California-based American Isuzu Motors Inc., Isuzu officials said.

However, at the behest of his superiors, one of the officials cautioned that the firm "is only conducting a feasibility study at this point."

"We are very serious about this. But there has been no final decision at all. We are proposing something. It could be scrapped at any moment," said Gary Major, advertising and merchandising manager for Isuzu Truck.

Isuzu, Japan's ninth-largest truck manufacturer based on 1983 truck registrations in that country, is the fifth Japanese auto and truck manufacturer to propose setting up assembly operations in this country.

Three of those Japanese manufacturers -- Honda Motor Co. Ltd., Nissan Motor Co Ltd. and Toyota Motor Corp. -- have followed through on their proposals.

Honda makes Honda Accord sedans in Marysville, Ohio, for East Coast distribution. Nissan assembles compact pickup trucks and subcompact Nissan Sentra passenger cars in Smyrna, Tenn. Toyota and General Motors Corp., through a joint-venture company called New United Motor Manufacturing Inc., soon will start producing front-wheel-drive, subcompact Nova passenger cars in Fremont, Calif.

The Novas will be marketed through GM's Chevrolet division. GM also owns 34.2 percent of Isuzu and is importing 29,500 Isuzu-made, Spectrum subcompact passenger cars for 1985-model year sales in 16 Eastern states.

Mazda Motor Corp. last March proposed building a U.S. plant to produce up to 250,000 subcompact passenger cars a year. Mazda officials said at the time that they were inspecting possible plant sites in Michigan and in the Southeast, and in the Mid-Central states of Iowa, Nebraska, Kansas and Oklahoma.

Isuzu officials yesterday said that they were looking at East Coast sites, including Baltimore and other locations in the Mid-Atlantic region, to assemble their 3.9 liter, 4-cylinder, KS22 urban delivery truck. That facility might also be used to assemble bus chasis components or low-volume specialty trucks, the officials said.

Isuzu Truck currently operates in 19 states through 70 dealers, four of which are in the Washington area. The company wants to add two more regional offices, one in the Northeast and possibly another in Dallas in the Southwest, to complement its regional offices now operating in Los Angeles in the West and Atlanta in the Southeast.

Isuzu's current U.S. ports of entry are in Long Beach, Calif., and Jacksonville, Fla. But the company plans to open two more ports -- one in Baltimore next month and another in Tacoma, Wash., on Nov. 27. An Isuzu "truck processing plant" -- essentially a facility to make relatively minor fixes on and additions to trucks delivered at port -- opened this month in Baltimore.

Isuzu officials, through Major, declined comment on how many commercial trucks the company plans to import and assemble for U.S. sales. "We are talking about a small operation, as far as volume is concerned, which is about all I can say," said Major, speaking of the proposed truck assembly facility.