The United States is conducting classified discussions with a number of Latin American countries that could add to the number of military facilities available for use in a regional emergency, according to Secretary of Defense Caspar W. Weinberger.

The existence of these discussions was revealed in largely overlooked public testimony by Weinberger last week before the House defense appropriations and military construction subcommittees.

There was no follow-up discussion by subcommittee members and Weinberger did not say what countries were involved. Sources indicated that Honduras in Central America and Colombia on the northern tip of South America are two of the nations involved, although there is no official confirmation.

The idea, according to government officials, primarily is to improve airfields in the countries involved so that if help is needed from the United States or other regional allies there will be places to land and refuel military aircraft.

The United States maintains a large naval and air base at Guantanamo Bay on the southeastern tip of Cuba. The Army's Southern Command--with land, air and naval facilities--is located in Panama.

The effort to expand the number of places where U.S. or allied forces might be able to operate from is a sensitive matter, according to government officials, because negotiations are not completed and because a number of countries in the region, while concerned about Cuban and leftist activities, are also worried about being too overtly identified with the United States or about the possibility of American intervention in the region.

The matter arose publicly when Rep. Bo Ginn (D-Ga.) asked Weinberger what efforts the Pentagon planned to counter Cuban expansion in the region and whether Weinberger envisioned the need for access to facilities.

Weinberger said the United States had facilities in that area and was working to improve them. While it would be useful to have additional bases, he continued, "basically we have essentially either the potential or the actuality of what we need to be of assistance in preventing the increase of communist aggression in that part of the world."

But when asked again by Ginn about future access "in this region," Weinberger added: "We have discussions under way, basically of a classified nature, that would enable us to add to the number of facilities that we see in the future we may sometimes need. Obviously, they are proceeding on a completely negotiated basis between sovereign countries. I think there is a full appreciation in a number of those areas of the importance of having facilities of this kind that can serve our mutual benefit."

The overall military construction budget request for fiscal 1983 totals $8.2 billion, including $45 million for so-called contingency facilities for the Air Force and $59 million for the Navy. It has not been stated publicly what those funds are for, though sources say the Navy money is primarily for construction work at Somalia and Diego Garcia in the Indian Ocean region.