Secretary of State George P. Shultz, in a speech suggesting the administration is adopting a less combative policy in Latin America, urged yesterday that major offensive weapons be banned from Central America and called on Argentina and Great Britain to negotiate a solution to the Falkland Islands dispute.

Though his speech to the annual assembly of the Organization of American States contained no specific new proposals, it was regarded as noteworthy by many Latin diplomats for confirming trends that have become increasingly evident in U.S. policy since Shultz took office last summer.

In Central America, while the administration remains determined to thwart what it regards as a communist-led effort to win control, the United States is dropping the belligerent Cold War rhetoric associated with Shultz' predecessor, Alexander M. Haig Jr. Instead, the administration has moved toward a lower-profile strategy of encouraging the region's democratic governments to join together and isolate their more radical neighbors, such as Nicaragua.

On the Falklands, the United States has decided over Britain's opposition to support Argentina's demand for negotiations. That is a conciliatory gesture apparently meant to overcome the anti-American sentiment that welled up throughout Latin America when the United States backed Britain during the war in the South Atlantic last spring.

Finally, perhaps reflecting his background as an economist, Shultz suggested there will be new emphasis on encouraging the Latin American countries to resolve the severe financial difficulties and trade imbalances that plague most of them. His stress on that subject followed predictions within the State Department that he intends to move U.S. foreign policy from a largely politico-military focus to a far greater concentration on international economic and financial problems.

These were the main themes addressed by Shultz in a speech that reflected his soft-spoken, low-key style. He began characteristically by saying, "I'm here more to listen than to talk," and he described his comments not as policy pronouncements but as "a few of my main reflections as I join this discussion among friends and neighbors."

Latin delegates said that, at a closed session of the assembly on Tuesday, Shultz' deputy, Kenneth W. Dam, warned of Soviet- Cuban threats to the Hemisphere in terms reminiscent of Haig's threats to "go to the source" in stopping Central American insurgent movements.

However, Shultz, while stressing that the United States remains concerned about the situation, made no denunciations of Cuba or Nicaragua, which the administration has accused of providing arms and other aid to leftist guerrillas fighting the U.S.-backed government in El Salvador. Instead, he called for negotiations among the region's countries to eliminate imports of offensive weapons and foreign military advisers.

"That may give us our opening," he said. "Why shouldn't we encourage the governments of Central America to agree, all of them, on a basis of reciprocity and strict verification, not to import major offensive weapons? . . . Why not go for agreement among Central American countries, again on a basis of reciprocity and verification, to reduce the numbers [of foreign advisers] to some low agreed level, or zero."

These are conditions that Washington has been trying for months to press on Nicaragua. During the summer, it switched to a so-called "regional context" approach of urging friendly democratic governments in the area also to press the Nicaraguans to agree on these points. And as Shultz reminded the delegates, at a meeting last month in Costa Rica six of these countries endorsed a framework for peace that echoed the American ideas.

President Reagan will visit two of these nations -- Colombia and Costa Rica -- when he goes to Latin America at the end of the month. U.S. officials privately acknowledge that they and Brazil, which is the other country on the itinerary and is in the process of returning to elected government, were chosen for visits as signs of U.S. support for Latin democratic forces resisting communist penetration.

Referring to the Falklands, Shultz said Washington backed Britain last spring because Argentina sought to take the islands by force and the United States "is not neutral on the overriding principle of peaceful dispute settlement."

But, he continued, "earlier this month we were pleased to support a balanced resolution [calling for negotiations] on the Falklands/Malvinas question in the United Nations." That caused resentment in British Prime Minister Margaret Thatcher's government, but Shultz implied yesterday that the United States is prepared to support a similar resolution when it comes to a vote in the OAS later this week.

Finally, Shultz spent considerable time addressing the hemispheric economic problems, which many Latin governments say are of greater concern to them than security issues. He said those countries, which are heavily in debt, should be prepared to take austere measures at home and to "restructure or, in exceptional cases, reschedule" their debts.

In return, Shultz continued, the United States will fight to give hard-pressed Latin governments continued access to financial markets and lending institutions such as the International Monetary Fund. He also pledged Reagan will give high priority to pressing Congress for passage of his Caribbean Basin Initiative designed to help countries of the region through financial aid, trade preferences and investment incentives.