The fighting in Zaire's Shabs province threatens to destory elaborate efforts by 98 U.S. and foreign banks to rescue that country from international bankruptcy in order to collect on massive loan payments that are long overdue.

Months of secret negotiations led to an unprecedented agreement signed in the ornate setting of the Bank of England last Nov. 5 by representatives of the world's leading commercial banks and Gov. Sambwa Pida Nbagul of Zaire's Central Bank. In return for a promise of stringent austerity and other tough conditions from Zaire, New York's First National City Bank (Citibank) agreed to lead a "best efforts" drive to raise $250 million more in international money markets to revive the African nation's economy.

Bankers Trust Co., Morgan Guaranty Trust and several other major banks were doubtful at the time of signing that the deal could be successfully implemented.The skeptics are much more pessimistic now that fighting has broken out in Zaire's copper-producing area. Even senior officials of Citibank, the sponsors of the rescue plan, say the new financing is impossible until the war in Shaba is satisfactorily settled.

Unless the country can be saved by a speedy military victory or a large new infusion of foreign aid, Zaire is likely to become the first nation in recent years officially to be declared in default of its debts to the world's commercial banks - in other works, officially bankrupt.

The financial collapse of Zaire - which owes $3 billion in foreign debts, including $500 million in commercial bank loans - could be absorbed without serious danger to any single lender or to the international financial system, experts believe. However, the impact and significance of a country going broke could extend far beyond the sums involved.

There is fear that a Zairian bankruptcy would be a blow to public and investor confidence in major commercial banks, which have made extremely large and still-growing loans to foreign governments and enterprises. Several major U.S. banks now make more than half their annual profits from overseas lending. The loans from big banks to little countries, many of them in questionable financial condition, have been a novel feature of the world economic scene since it was thrown into disorder three years ago when the Organization of Petroleum Exporting Countries (OPEC) in the Middle East raised prices.

Zaire's troubles also illustrate the potential foreign policy impact of private overseas investments. While New York bankers maintain that they ask no favors of the U.S. government in protecting their financial stakes in Zaire, there is no doubt that the presence of American private capital is a factor in Washington decision-making.

In asking Congress 18 months ago to approve $60 million in emergency economic aid for Zaire, Edward W. Mulcahy, then deputy assistant secretary of state for African affairs, prominently cited the threat to U.S. financial interests as a reason. In the current troubles, both Washington and Wall Street are well aware that the private investments in Zaire were undertaken with explicit U.S. government encouragement. As late as last July, when Zaire was far behind in its debt payments and in severe economic difficulty, the U.S. embassy in Kinshasha publicly declared that the country "continues to offer good prospects to the farsighted supplier and investor."

Citibank's specialist on Zaire, Vice President Hamilton Meserve, has been spending one day each week in Washington recently exchanging views and information with the State and treasury departments, World Bank, International Monetary Fund and other agencies. Meserve said he speaks almost daily by telephone with "my counterpart," the State Department's Zaire county director, Edward Marks. At least a dozen U.S. banks are regularly in contact with the State Department about Zaire.

There is "reasonable coordination" between the banks and the government, a State Department official said. "Our interests are not identical, but they are not opposed and they are not separate!"

Former U.S. officials in Zaire play significant roles on behalf of private business. The former CIA station chief i Kinshasha, Larry Devlin, who is reputed to have helped install President Mobutu Sese Seko in power in 1965, is the Zaire representative for New York entrepreneur Maurice Tempelsman, reportedly for close to $100,000 yearly.

A former U.S. ambassador to Zaire, Sheldon B. Vance, a vocal exponent of aid to Zaire while in U.S. service, was given VIP treatment by Mobutu's government when he traveled to Kinshasha last month as a private lawyer and consultant for business clients whom he refuses to name. Informed sources said one of the clients is Pan American World Airways, which is on the verge of losing its contract to operate Mobutu's "Air Zaire."

Known as the Belgian Congo before obtaining independence in 1960, Zaire is a potentially rich and strategically important country about the size of the United States east of the Mississippi. Bordering on nine other states including Angola, it has been a focal point of U.S. policy and U.S. interests in Southern Africa in recent years.

Zaire is reported to have 74 per cent of the world's industrial diamond reserves and 28 per cent of the known reserves of cobalt. (The United States imports nearly all its cobalt, which is essential to the metals, space and nuclear power industries, and about half the imports came from Zaire). In addition, the country has enormous deposits of copper - its major export - and of many other ores.

Beginning about 1970, Mobutu led the country into an ambitious program of development - and of borrowing and spending outside money. "Calling all American investors, industrialists, merchants," proclaimed Zaire's full-page ads in U.S. publications offering "unprecedented opportunities to extract and process its fantastic mineral resources" and other chances to make money.

Dozens of major U.S. firms responded, backed up by government-guaranteed loans from the Export-Import Bank and commercial loans from their private bankers. Starting with a 1970 syndicated loan led by New York's Bankers Trust, the private banks also extended large "balance of payments" loans to Zaire's government - in effect, direct support for the national treasury which has been controlled personally by Mobutu.

The bubble burst in 1975 with a nosedive in the world price of copper and the closing of Zaire's best outlet to markets - the Benguela railroad running through war-torn Angola. With little foreign money coming in, Zaire stopped making payments on the massive debts it piled up during the spending boom. Banks seeking to collect often received no reply at all to increasingly insistent inquiries about the payments due.

Last June officials of 11 governments including the United States met at the French Foreign Ministry to "reschedule" the debts Zaire owed to their national treasuries. This "Paris club" agreement allowed Zaire a delay of up to 10 years in payments due in 1975 and 1976 to the foreign governments. The agreement did not cover Zaire's debts to commercial banks, although a clause reportedly promised (to the bankers' discomfort) would be made "on a comparable basis."

The 13 "agent banks" which had led the way in arranging Zaire loans by 98 banks worldwide sent a joint telex to Zaire last August demanding a meeting with government officials to discuss their money. The agent banks - six American, three French, two British, one Belgian and one Japanese - had organized in London four months earlier to press their case together. The loans involved in these discussions totaled $375 million, most of them to be repaid in the middle and late 1970s.

Early last September the agent banks' representatives met secretly in London for the first time with Zaire's officials headed by its Central Bank governor, Sambwa. To the bankers' dismay, Sambwa asked for an even better deal than the creditor governments had given him - not 10 years but a 15-year "rescheduling" of all Zaire's private bank debt.

Many of the bankers felt there was no way to avoid a rescheduling - a confession of bankruptcy - although some hoped to get part of their money early as the price of an overall agreement. There was little precedent to guide them. According to Institutional Investor, a financial publication that told the story of the talks in a recent issue, it was the first time that private bankers had sat down to negotiate with a defaulting sovereign borrower.

A series of meetings in London and Paris culminated in a two-day session in New York's St. Regis Hotel last Oct. 21-22. There Irving Friedman, the senior international adviser for Citibank and a prestigious veteran of an earlier career at the World Bank and International Monetary Fund, stunned the other bankers by disclosing that he had worked out a tentative deal with Sambwa.

Zaire would have to accept strict economic policies and management reforms required by an IMF "stabilization program" and would have to pay the back interest and principal which it owed (close to $150 million by early this year). In return, Citibank would lead an effort to rasie $250 million in new capital for Zaire. Friedman insisted then and continues to insist that the new money would be used to rejuvenate the economy rather than pay the old debts, but some of the other bankers ridiculed this.

The advantage of the Friedman plan, which was finally accepted after much controversy, is that Zaire would avoid an admission of bankruptcy, saving that country from being cut off from future loans and saving the commercial banks and their international lendings from public embarrassment. The disadvantage was doubt that Zaire would faithfully fulfill the conditions, more than Citibank could find investors willing to put up $250 million for its part of the deal.

Early this year, Mobutu signed a letter accepting IMF economic conditions, which included sharp cuts in government spending and a tight money credit policy. A short time later the fighting in Shaba began - throwing Mobutu's budgetary plans and his very survival as a leader into doubt.

On March 17, despite the Shaba fighting, Friedman and Citibank's Meserve flew to Zaire to see Mobutu and other leaders. Following the 10-day visit, Friedman sent a communique to his fellow banks saying, "it would appear that the success of [Mobutu's] economic program hinges on the outcome of the Shaba affair."

A series of international economic decisions involving Zaire is now pending, most of them deeply affected by the Shaba fighting. Last week the staff of the IMF sent to the monetary fund's governing board the "stabilization program" which Mobutu signed before the Shaba fighting, with a recommendation that the plan be accepted and new "standby" funds granted.

Later this spring, the French are expected to summon another "Paris club" meeting of Zaire's governmental creditors to postpone scheduled payments on that country's official debt for 1977.

This summer, perhaps in June, the World Bank plans to convene a separate meeting of potential donor nations to contribute new development money for Zaire. The United States, France and other nations with a stake in Zaire are behind this effort to raise additional funds.

According to a New York commercial banker, Washington officials recently rejected the idea of another emergency inoculation out of the federal budget because "it might be seen as a bailout of the commercial banks." That was before the fighting broke out in Shaba, however, and that conflict has changed many perspectives. Among other things, nobody seems certain who is going to pay for Mobutu's side of the war. Despite their major investments, the New York bankers and their counterparts in Paris, London, Brussels and Tokyo are unprepared to do so.