In a move that opens up expansion opportunities in Latin America, the Global Alliance consortium involving American President Lines and three other carriers is upgrading its Asia-U.S. East Coast service from a 10-day to a weekly schedule.

It is the first significant expansion of the service since the four carriers launched their all-water route through Panama in March. The move will

allow the carriers to strengthen their services between Asia and Venezuela, Colombia and the Dominican Republic.In addition to creating a weekly rotation, which will involve increasing the number of ships in the service from six to nine, the carriers have added regular port calls at Puerto Sucre, Venezuela.

A Global Alliance-operated feeder service now connects Colon, Panama, the carriers' Latin American transshipment center, with Puerto Cabello, La Guaira and Puerto Sucre in Venezuela, Cartagena, Colombia and the Dominican Republic.

Each of the alliance partners, which also includes Orient Overseas Container Line, Mitsui O.S.K. Lines and Nedlloyd Lines, has been allocated space on the feeder services into and out of Colon.

The U.S. East Coast-Asia service picks up Latin American freight at Panama and takes it to to Asia. John Urban, APL's newly named Central and South America vice president, held out the possibility that some time in the future the service may move freight between the U.S. East Coast and Latin America as the carriers evaluate other ways of expanding the scope of the all- water service. Currently, no U.S. East Coast freight bound for Latin America travels on the alliance ships in the U.S. East Coast-Asia lane.

''We're looking at a number of opportunities and that is one we are studying," Mr. Urban said in an interview.

''Clearly we are looking to grow throughout the region," he said, adding that the focus during the next year will be on strengthening APL's presence in the north coast of South America and in the Caribbean.

APL said that one of its first accounts in the service is Toyota Motor Corp., for which the Oakland carriers will be transporting auto parts from Nagoya, Japan, to the Toyota de Venezuela assembly plant near Puerto Sucre.

Toyota's auto part shipments, which will begin with a mid-September sailing, reflect further inroads by containerization into a trade that until now has been dominated by breakbulk, said John Urban.

APL said it also is moving auto parts for Ford Motor Co. into Puerto Cabello, Venezuela, from South Korea and Japan. APL and its partners are using the service as a springboard to enter the Asia-South America trade.

Four MOL ships, three OOCL ships and two Nedlloyd ships will comprise the nine vessel Asia-U.S. East Coast service. By early next year, the four carriers will be sharing space on 67 vessels in the trans-Pacific, Europe-Asia and Asia-U.S. East Coast service.