U.S. officials say they have received reliable intelligence that the Marxist Sandinista government of Nicaragua, through a covert arrangement with the military dictatorships of Chile and Panama, has obtained cluster bombs to drop on U.S.-backed contra guerrillas.

The officials said their information is that Nicaragua and Chile, which do not have diplomatic relations, have used Panama as middleman in the transactions that began three or four months ago. The officials said Panama purchased an unspecified number of cluster bombs from Ferrimar, a Chilean armaments manufacturer with close ties to Chile's military government, then transferred them secretly to Nicaragua.

Cluster bombs spread shrapnel over a wide area. Many human rights and disarmament activists have denounced their use as inhumane. The United States stopped sending them to Israel following charges that Israel improperly used them during the 1982 invasion of Lebanon.

Spokesmen here for the three countries said they had no information about such a sale but that the story sounded improbable.

Bosco Matamoros, a contra spokesman contacted in Central America, said contra forces inside Nicaragua had recovered several canisters from cluster bombs used against them by Nicaraguan government forces in bombing raids Oct. 7, 8 and 10. He added that Cyrillic alphabet markings indicate the bombs were Soviet-made, and he said he was not aware of any evidence that Nicaragua is using similar weapons made in Chile.

U.S. officials, while declining to offer specific information, insisted that the cluster bomb sales took place. They also said the United States is certain that Chilean-made cluster bombs were used in recent air attacks against the contras by Nicaraguan-owned Soviet Antonov AN26 transport planes.

The officials cited the alleged arms transfer as the most dramatic example of what one called "a pariahs' international" in which various Latin American authoritarian regimes cooperate with each other despite wide ideological gulfs.

Nicaraguan President Daniel Ortega and key Sandinista government leaders are acknowledged Marxist-Leninists with close ties to Cuba and the Soviet Union, while Chilean President Augusto Pinochet is a staunch anticommunist. Panama's military strongman, Gen. Manuel Noriega, has close personal ties to Ortega and Cuban President Fidel Castro, and Noriega's opponents charge that he is involved in wide-scale corruption and narcotics trafficking.

According to U.S. officials, the incentives for cooperation among these three countries and another rightist military dictatorship, Paraguay, include their increasing isolation in a region where the trend is toward democracy, and a shared hostility toward the United States.

In addition to openly providing military support to the contras, the Reagan administration has become increasingly critical of repression in Chile and Paraguay, and last summer aligned itself with reformist forces in Panama seeking to oust Noriega.

Since the Pinochet government came to power in a bloody 1973 coup, Chile has had close political, military and intelligence ties with Paraguay's President Alfredo Stroessner. That relationship has increasingly included Panama. The officials said that the Chileans recently hosted an ambassadorial-level meeting of these three countries and South Africa to discuss intelligence-sharing and dealing with U.S. criticism.

South Africa, although far removed from Latin America, has maintained close military and intelligence liaison with Chile and, to a lesser extent, with Paraguay.

Contact between Chile and Nicaragua has been more sporadic because of ideological differences, distance and the absence of diplomatic relations, the officials said. But, they continued, it has increased in the past year or two, partly at Noriega's instigation, and has included an understanding that the two countries will not criticize each other publicly. The officials said Chile and Nicaragua also have set up a system of secret meetings periodically in Panama and other countries.

After the United States cut off military sales and aid to Chile in 1976, the Pinochet government encouraged two privately owned firms in Santiago, Ferrimar and Cardoen Industries, to begin manufacturing weapons for the Chilean armed forces. Both companies later branched into export sales, and Cardoen has been very successful, selling cluster bombs and other items to various countries including South Africa. Its largest customer is Iraq, which is estimated to have bought about 95 percent of Cardoen's cluster-bomb production last year.

Ferrimar, much less commercially successful, also makes cluster bombs tailored to the requirements of Third World countries. The officials said the United States was drawn to close scrutiny of Ferrimar's activities by discovery early this year that the company was selling the bombs to Iran.

The officials said the sales to Iran appear to have been halted last summer. But, they added, about the same time, the United States discovered that some cluster bombs were being purchased by representatives of the Panamanian government and flown to Central America. The officials said that one gap in U.S. information involves whether the bombs were transported directly to Nicaragua or were picked up by the Nicaraguans in Panama.

Adolfo Arrocha, acting head of the Panamanian Embassy here, noted that Panama is headquarters for thousands of foreign companies acting as agents in international transactions. But, he added, all explosives brought into Panama are kept under tight government controls, and he said he was not aware of "a shred of evidence" that his government was involved in getting armaments to Nicaragua.