The meeting here this week of the military presidents of Brazil and Argentina appears to have moved the two regional giants from past estrangement toward cooperation.

A communique after the summit Thursday between Gens. Reynaldo Bignone of Argentina and Joao Figueiredo of Brazil said they had agreed on a course of cooperation to confront international economic difficulties.

Brazil has failed to maintain payments on its foreign debt of $80 billion while Argentina--with a population of fewer than a quarter of Brazil's 125 million--is negotiating a rollback of its $43 billion debt.

The encounter between Bignone and Figueiredo comes after years of strained relations caused in part by the construction of the massive Itaipu hydroelectric dam near the site of the talks.

The ceremonial justification was initiation of work on a $32 million bridge over the Iguacu River that divides their countries. They share the massive Iguacu Falls, which dwarf Niagara and are a tourist attraction for both sides.

The two leaders also signed an agreement allowing Argentina to buy Brazilian electricity. At full production, Itaipu will be the world's largest producer of electricity.

Both presidents were chosen by a small military elite to rule their countries. Bignone reminded Figueiredo of his intention to be "the last Argentine president not to be elected by the choice of the people." Elections are due late this year.

Spokesmen said Bignone made clear his approval of Figueiredo's smooth handling of elections last year, in effect ending 18 years of military rule. An electoral college is to choose the next president.

Brazilian Foreign Ministry spokesman Bernardo Pericas said Figueiredo had not--as his ministers had forecast--raised the subject of Brazilians missing in Argentina since that country's repression of opposition in the late 1970s.

But on the day of the talks Sao Paulo's archbishop, Cardinal Paulo Evaristo Arns, announced the most comprehensive list yet of citizens missing in Argentina. The list of 7,791 names--compiled by Sao Paulo's Committee for the Defense of Human Rights in the Southern Cone--is to be presented to Pope John Paul II on Monday.

Committee spokesman Jaime Wright said the list was achieved at considerable risk to researchers and documented at least 1,000 more names than earlier efforts. But he estimated the real number of the missing at 15,000.

Argentine Foreign Minister Juan Aguirre Lanari said the main subject of the two presidents was his country's dispute with Britain over the Falkland Islands. In a speech, Figueiredo reaffirmed Brazil's support for a negotiated settlement with Britain and said "our solidarity is not just a rhetorical concept."