When Pope John Paul II visits Paraguay next month, the eyes of the world will focus briefly on the dictatorial regime of Gen. Alfredo Stroessner. Opposition leaders and Catholic officials will seize the moment to put some heat on Stroessner, according to recent U.S. intelligence reports.

The CIA believes the recent relaxation of Stroessner's iron fist is merely an attempt to placate the populace so there won't be any trouble during the pope's visit.

This is the pontiff's first visit to the landlocked country of 4 million and comes on the heels of the seventh rigged presidential reelection of Stroessner, who began his rule in 1954.

The 75-year-old Stroessner is a despotic dinosaur. He and Chile's Augusto Pinochet are the last of their kind in Latin America. Only North Korea's Kim Il Sung has ruled longer as a dictator than Stroessner.

Stroessner came up through the military ranks. When he had seen enough coups, he staged his own in 1954. A secret CIA report says Stroessner had gotten a grip on the army and the Colorado political party. Anyone who opposed him was jailed or exiled. ''By the early 1960s, it was apparent that personal loyalty to the president was necessary -- and in many cases sufficient -- to obtain or to keep any important government post,'' according to the report.

''Stroessner is much like a stereotype Latin American dictator. Elections are rigged, opposition parties are kept dispirited and fragmented, the congress is a rubber stamp for executive decisions, and the constitution is regularly rewritten to permit Stroessner to remain in office.''

Stroessner has retained his power for so long because he turned the century-old Colorado Party into a patronage system. He has kept his family, his friends and other loyalists happy by corrupting them all.

''Contraband flows freely across Paraguay's border,'' the CIA notes in its secret Stroessner overview, ''and graft in the form of illegal concessions is one means Stroessner uses to reinforce loyalty.''

Paraguay may be the only country in the world whose contraband trade of exports and imports is greater than its legal trade. Stroessner loyal-ists live in luxury on profits fromthe smuggling trade in alcohol, cigarettes, perfume, computers, cotton and a myriad of other items -- including, increasingly, cocaine and other drugs.

The Stroessner millionaires inhabit the luxurious Las Carmelitas suburb of the capital city of Asuncion. General Andres Rodriguez, commander of the First Army Corps, lives in a replica of Versailles that he had built. Stroessner's son, Alfredo, built a replica of the White House.

No wonder that for more than three decades Paraguay has been a haven for every kind of thug who can pay Stroessner's price: Joseph Mengele, the evil angel of death from Auschwitz prison, and other Nazis; Georges Watin, who tried to assassinate Charles de Gaulle; the late Nicaraguan dictator Anastasio Somoza, who was blown to smithereens by a bazooka in Asuncion in 1980; Auguste Ricord, a notorious narcotics dealer of ''French Connection'' fame; and a veritable rogues gallery of other assorted scum.

While such are welcome in Asuncion, the courageous, outspoken U.S. ambassador there, Clyde Taylor, is treated as persona non grata. He has been subjected to vitriolic attacks in the Stroessner-owned media. Stroessner's ex-son-in-law, Humberto Dominguez Dibb, has twice threatened in his government-run newspaper to burn down the U.S. Embassy. And Taylor has the dubious distinction of being the only U.S. ambassador to have been deliberately gassed by a government. That happened in February 1987 when police kept 300 guests from attending a reception given in Taylor's honor by an opposition group. The police held back the visitors, and tear-gassed a garden where Taylor sat with 30 other guests.

American pressure to reform has been felt by Stroessner, but with minimal aid going to Paraguay, the United States has few levers to pull. More pressure has been applied by the democratization of Latin neighbors.

But the pope's visit puts even greater pressure on Stroessner to reform. CIA sources told us Stroessner has relaxed his oppressive rule and initiated a mini-glasnost in recent months. The number of political prisoners is down. Tales of police torture have also diminished.

The pope is not Stroessner's biggest problem, though. ''Like most strong men, he refuses to groom anyone to take his place,'' the secret CIA report says. ''The major threat to Paraguay's stability, therefore, is the possibility of Stroessner's sudden death.''