Not since 1975, when Gen. Francisco Morales Bermudez staged a palace coup that overthrew his military predecessor halfway through an international conference being held here, has Lima been filled with as many foreign dignitaries as it is this weekend.

The presidents of Columbia, Venezuela, Costa Rica and Panama are already in Lima or are coming Sunday. The spanish prime minister, Adolfo Suarez, is en route from Madrid and Rosalynn Carter arrived this evening from Washington.

Even Lord Trefgarne, Queen Elizabeth's lord-in-waiting, will arrive in time to see Fernando Belaunde Terry sworn in Monday afternoon as Peru's 102nd president. The ceremony will be rich in irony for Peru and filled with implications for the rest of Latin America, where military governments from Guatemala to Chile are under pressure to hold elections and return their countries to civilian rule.

Monday's transfer of power here from morales Bermudez to Belaunde, 67, an architect-politician who won a resounding victory in elections held in May, may also be reflected in this fall's presidential race in the United States.

The republican platform and Ronald Reagan's foreign policy advisers are deeply critical of the Carter administration's policies backing human rights and democracy in Latin America, policies that have alienated the United States' military allies in countries such as Argentina, Chile, Uruguay, Paraguay and Bolivia.

Rosalyyn Carter's role as head of the U.S. delegation to Monday's inauguration signifies the importance that her husband's administration attaches to Peru's return to democracy after 12 years of authoritarian military rule -- as does a $100 million-a-year U.S. aid program and Washington's recent help in persuading the World Bank and the Inter-American Development Bank to reverse lending to the new Belaunde government.

"I'd say we're immensely encourage by what has happened here," U.S. Ambassador Harry Shlaudeman said in an interview this week. "The policy of this administration from the outset has been to promote and support democratic governments in Latin America, which is exactly what we've done in Peru.

"Of course," he added, "the Pervian government and people are the onese who have done it."

What Shlaudeman refused to discuss on the record were the subtle steps the Carter administration took to ensure that the military here stuck to the timetable Morales Bermudez announced three years ago, a timetable that was threatened at various times along the way by junior military officers who [TEXT OMITTED FROM SOURCE] throw Morales Mermudez, just as he wanted to keep their power and overthrew his predecessor, Gen. Juan Velasco.

Particularly galling for some of the officers is that Belaunde, the very man who was overthrown by Velasco in 1968, won the recent election and will resume the presidential office he was forced out of 12 years ago. Not one of the country's current military leaders, including Morales Bermudez, will attend Monday's inauguration, partly out of pride and partly because of fears that the generals would be booed and embarrassed if they attended.

Despite their absence, however, neither diplomats nor Belaunde's own people believe the military will attempt to stop the transfer of power or interfere with the new government.

Velasco came to power at the head of a leftist military government that expropriated the holdings of U.S. oil companies and other foreign interests as well as Lima's major newspapers and the great sugar estates of Peru's traditional oligarchy. There was brave talk then of a social and economic revolution sufficient to end this country's status as one of the poorest and least socially advanced in Latin American.

But the current crop of generals knows that the military government failed to engineer the economic growth that Peru's 18 million citizens expected. They also know that the military as an institution became increasingly discredited and unpopular because of the government's authoritarian style, widespread corruption, administrative incompetence, high unemployment and an annual inflation rate now galloping along at 70 percent.

The military's agrarian reform program, while initially popular, foundered for lack of technical assistance and credits, forcing Peru to import costly foodstuffs it once produced for itself. The nationalization of foreign companies scared away foreign capital while the state-owned companies created by Velasco, including the vitally important petroleum and mining companies, are poorly managed and virtually bankrupt.

According to Manuel Ulloa, who will serve as Belaunde's prime minister and direct the Finance and Economics Ministry, the new government will move very quickly to implement policies aimed at spurring employment and agricultural production, reducing inflation, encouraging foreign investment, infecting private capital and competent management into the state-owned companies, restoring freedom of the press by returning the newspapers to their former owners and attempting to end the corruption that now prevades all levels of government here.

"We've got to be forceful. We've got to exercise authority and not dilly-dally. The people understood that they had to give us -- and they gave us -- a clear majority in order to govern," Ulloa said in recent interview. The May election results gave Belaunde a surprising 45 percent of the popular vote and a majority in both houses of the new Congress.

Besides jobs and agriculture, Belaunde wants to restore an independent press and judiciary to create the checks and balances necessary for responsive, democratic government and to guard against the corruption that became prevalent during the years of military rule.

As in all Latin countries, though, perhaps the new government's most important task and most difficult challenge will be to establish rapport with the military to avoid another coup.

"Obviously, we've got to help the military depoliticize in order to promote the more constructive role it can play in society," Ulloa said.

Among other things, the Belaunde government wants to remove the justifications the military here used over the last decade to spend billions of dollars on tanks, ships and fighter planes. Ulloa said the new government's foreign policy will concentrate on seeking peaceful solutions to a series of border conflicts among Peru and neighboring Chile and Ecuador as well as between Argentina and Chile and between Bolivia and Chile that have given Peru's generals the excuses they needed to arm themselves to the teeth.

"I think in countries like ours, if we could spend half the money we do on arms expenditures, we could be a lot more efficient and have a lot more money for economic development," Ulloa said.