Peru Central Bank will run out of money to pay the country's foreign bills by June 1 at the latest highly placed financial sources here say.

The resulting default, sources said, could come as soon as next month as loan installments owed U.S. and other foreign banks come due.

The impending financial collapse is expected to plunge the military-ruled country into an economic and political crisis that may endanger elections scheduled for June, the first to be held here in 15 years.

On Friday, sources here said, a consortium of major U.S. and other international banks tentatively turned down a last-ditch Peruvian proposal to refinance the $306 million Peru is supposed to pay them this year.

The sources said the banks apparently based their decision on the negative findings of an International Monetary Fund investigating team sent here last month to determine if the Peruvian government was living up to an economic austerity program it agreed to last fall.

While an informed banking source said in a telephone interview from New York that the IMF findings had not been encouraging, he denied that the foreign banks, including many of the largest U.S. institutions, had made a firm decision or had broken off talks with Peru.

Instead, he suggested that the desperate Peruvian government, seeing it precarious economic "house of cards" about to collapse, may be trying to pressure the banks by publicly putting the ominous specter of default and subsequent chsos, on their shoulders.

Peru is one of about 75 developing countries, hard hit by international recession, that have borrowed hundreds of billions of dollars over the past several years from private banks, most of them in the United States.

The prospect of massive defaults frightens both the banks and major Western governments, giving the troubled countries leverage in getting additional resources to stave off economic collapse. Peru's situation was preceded last year by a similar war of nerves with Zaire.

None of the banks, which normally find the Third World loan business profitable, wants to see a precedent-setting default. But at the same time they question how long they can continue extending massive loans.

Although both the banks and Peru say no loan installment deadlines have passed without payment being made, both agree that Peru's present financial crisis is "infinitely worse" that at any time during the past several years of near constant economic trauma and steady downhill slide.

Without the now-endangered refinancing, it is only a matter of time - perhaps within the next severals weeks - that default is expected to occur.

The $306 million that Peru owes to the private banks is only a part of the $1 billion foreign debt due this year. It is the most important part, however, since the rest is owed to other governments and international institutions that can presumably be persuaded to postpone demands for pay.

Sources here said the most immediate internal results of default to the banks would include political upheaval beginning with a Cabinet shuffle. They predicted the possible replacement of moderate President Gen Francisco Morales Bermudez with a hard-line military faction that could use economic priorities as an excuse to suspend the scheduled June 4 election for a constitutional assembly.

More seriously, from the point of view of most Peruvians, the banks could cut off short-term lines of credit that pay for the food imports supplying more than half of Peru's needs.

Peru's problem is a matter of simple arithmetic, a financial source here said. The Central Bank, Peru's government repository for all foreign funds entering the country, currently has no reserves and is living a day-to-day existence.

The June 1 time frame, he said, is arbitrary: the outside limit for postponing payments due and scraping together loose change.

While other experts here might quibble with the precision of his figures, and the government considers the exact amounts something of a national secret, no one denies that Peru is repidly approaching the bottom of its financial barrel.

How it got to that point is a matter of some discussion, and has a definite bearing on the course events will take during the next several weeks.

The banks believe that the military leaders, despite their generosity and patience with a struggling economy, have squandered much of Peru's resources, and wasted money on themselves, and ill-conceived, badly managed social reform programs.

They also believe the government has lied to them about how it spends money and about its intentions to get its financial house in order.

Under similarly desperate circumstances in 1976, Peru asked the banks for $400 million to refinance loans due that year.

While admitting that the situation looked serious at that time, one New York banker involved in those negotiations said the "man reason" the loan was approved was "to perpetuate Morales Bermudez in power." He said the banks considered Morales Bermudez, a former Peruvian finance minister, to be their best bet to get back the money they had already put into the country.

Several months later, in the fall of 1976, the Peruvian military agreed to purchase $250 million worth of fighter planes from the Soviet Union. The banks, which said neither the Soviet planes, or any other weapons expenditures, had appeared in the budgets Peru had submitted in the loan application, were outraged.

"It looked as if we were giving them money to support the Soviet arms industry," one banker said.

Shortly thereafter, it became apparent that the 1976 "last ditch" loan, despite Peru's promises of better organization and austerity, had done little to get the country back on its feet. Throughout 1977, Peru's economic situation worsened.

"What did we perpetuate?" the New York banker asked. "The whole damn place has gone to hell."

The Peruvian government has a different version of events.

As recently as four years ago, government Peruvian oilfields promised massive reserves and the price of copper, Peru's major export, was soaring, the banks fell all over themselves trying to give Peru money.

At that point, no one seemed to care that Peru, which has a gross national product of about $12 billion a year, was becoming dangerously overextended.

Today, the projected oil reserves have been proven greatly overestimated. The prices of copper and sugar, another majot export, have dropped markedly; and the rivers of anchovies, whose offshore abundance once provided a major source of Preuvian income from fishmeal, have mysteriously disappeared.

Now, in this view, just when the military has decided to return the country to civilian government, greatly pleasing the human "rights" conscious Carter administration, Peru feels that its once-eager banking friends, most of them in the United States, have turned traitor and lost their patience during temporary hard times.

While Peru shows a certain disappointment with the banks, however, it places much of the blame for its current problems on the IMF, which Morales Bermudez, in an interview last week, called an "anachronistic institution" that deals in "economic arithemtic" rather than Third World reality.

In exchaged for loans to developing countries, the IMF often insists that governments conform to strict budget programs. The Peruvians found the IMF's economic "suggestions" for spending cutbacks so unpalatable that on two occasions, in 1976 and mid 1977, they broke off loan negotiations.

When it became clear last fall that Peru was going to be unable to meet its 1978 debt commitments, Peru went to the IMF on its knees.

In exchanged for a $100 million Fund loan, Peru agreed to a harsh austerity plan that sources here now say was not only unrealistic but was imposed by the IMF in what they believe was a form of retribution.

The main importance of the IMF loan for Peru was not the relatively insignificant amount of money involved, but the IMF seal of approval to present to the commercial banks when the time came. When Peru finally went to the banks in January, after being turned down by the U.S. Treasury for an emergency $100 million, the banks not unexpectedly pegged their refinancing approval to Peru's compliance with the IMF program.

Last month, an IMF investigating team went to Peru for a regular check on that compliance. According to sources here, the team found that virtually none of the austerity plans major goals had been met.

Morales Bermudez said that he does not object to the austerity goals, but that Peru simply needs longer than the two years outlined by the IMF to achieve them.

Asking for "international cooperation" and obviously aware of the Carter administration's desire for him to continue with his plans to return the country to an elected civilian government, Morales Bermudez, warned that further financial pressure would prejudice "the preservation of human rights and political liberties."