Automobile imports still outnumber exports by more than 4-to-1, but for many U.S. ports, the cutting edge of their marketing efforts to the auto trade are now focused on attracting exports.

The reasons relate to the growing number of foreign and joint U.S.-foreign assembly plants in the United States, and greater access to foreign markets by U.S. automakers because of the weak dollar. Those factors are drawing ports' attention to the export market's potential."There is a trend toward export of automobiles in the U.S.," said John Cushing, marketing manager at the Port of Los Angeles. "We're seeing fewer and fewer imports because of the transplants that are here in the U.S. now and the requirements that these manufacturing plants have to meet U.S. domestic demand."

The value of automobile exports at the Port of Baltimore, the nation's largest export port for autos, surged 38 percent last year to $1.78 billion, with Chrysler accounting for some 66 percent of that figure. Exports at the Port of New York and New Jersey, the second-largest export port, grew 13 percent last year.

''Exports have increased and will continue to increase," said Don Wylie, director of trade and maritime services at the Port of Long Beach.

Exports from vehicles assembled in the United States by Toyota, General Motors and Chrysler account for about 60 percent of all the automobile trade moving through the Port of Benicia, Calif., a privately held facility that was the nation's third-largest auto export port last year.

The long-term potential for growth in automobile exports has many port authorities, including Los Angeles, talking regularly to existing and new automobile accounts about facilities required to handle exports.

''With our existing customers we have discussed routing export autos through our port," Mr. Cushing said. "We have discussed with them what would be required of us as a port in terms of storage and staging areas, and the railroad's requirements for the railcars."

Competition among ports to handle auto exports may be heating up in some areas, including the Bay area, where the Port of Richmond is looking to expand its presence in the automobile trade for both imports and exports.

''We're looking all the time to gain market share," said James Faber, operations manager at the port, which is just to the north of Oakland. The decline of the dollar is probably the largest factor enabling U.S. automakers to boost exports. The low dollar also has led to a growing volume of exports

from the eight foreign and joint-venture assembly plants now in operation in the United States.

Those plants were originally created to allow Japanese automakers greater access to the U.S. market by hiring U.S. workers. But with the yen's skyrocketing appreciation, those plants have become low-cost operations by Japanese standards, needed to support those automakers' global demands.

The growth of auto exports, therefore, is partly explained by the eight foreign plants now operating in the United States. Together, those plants exported 172,000 units in 1993 including to Canada, according to the Japanese Automobile Manufacturers Association (JAMA).