Ever since Treasury Secretary James A. Baker III unveiled his $29 billion plan to stimulate the ravaged economies of many debtor nations, world attention has focused on whether commercial banks are willing to boost their lending to these nations during the next three years.

But the most difficult part of the so-called Baker initiative might not be persuading banks to make the loans. It may be finding debtor nations to take them.

The so-called Baker initiative envisions a modest increase in lending to debtor nations that are willing to take steps to reform their economies -- such as removing roadblocks to foreign investment, reducing the number and size of state companies or monopolies, or subjecting long-protected private industries to the rigors of international competition.

Many Latin American officials said that vested interests, the long history of state domination of many economies and the historic aversion of former colonies to foreign investment will make it difficult for them to undertake, at least in the short run, many of the reforms the Baker project envisions.

"One of the key questions that has yet to be tested is the willingness of the debtor nations to move more forcefully toward free markets," according to a key official of a giant commercial bank.

However, the bank official said, if ever there was a chance for many of these countries to change their economies, the time might be now. There appears to be more receptiveness to major economic reforms now than at any time in recent years, he said.

"Chile and Ecuador are selling off some state companies. Argentina and Brazil are talking about it. The Mexicans have sold off a state hotel chain," the official said.

The International Monetary Fund played the pivotal role in the first years of the debt crisis. It required countries to take wrenching steps to wean themselves from foreign borrowing, to learn to live within their means, so to speak. In return, commercial banks and the IMF itself lent the countries new funds to ease the transition, and the banks rescheduled the repayment terms of outstanding debts.

Under the Baker proposal -- which still is in the working stages -- the international leadership would shift from the IMF to the World Bank and, to a lesser extent, the Inter-American Development Bank.

The multilateral banks have been concerned with economic development, while the IMF's focus has been "stabilizing" countries in economic crisis.

World Bank teams already are at work analyzing the economies of the various debtor nations, hoping, with the aid of officials of the countries themselves, to identify economic reforms that could be supported by increased lending from the development banks and the private commercial banks that hold the bulk of the debt in Latin America.

Under the Baker proposal, the development banks would increase their lending by about $9 billion during the next three years -- to a total of nearly $20 billion -- and the private banks would kick in with $20 billion more.

William R. Rhodes, the Citibank executive who has played perhaps the most prominent in the Latin American debt crisis of any American commercial banker, said many developing countries "have made substantial progress over the past three years addressing their balance-of-payments problems. We are now looking forward, with the Baker initiative, to helping them complete their return to the voluntary lending market."

The countries would use the funds promised under the Baker initiative to invest in new plants and equipment and to buy the additional imports most countries require to boost economic production. Most developing countries must import a wide variety of components, raw materials and spare parts to keep their industries going. That is one of the reasons debtor nations suffered recessions when governments adopted policies to restrain imports to make dollars available to pay debts.

The Baker plan would increase the amount of dollars available to debtors -- so they could pay their debts and grow.

The Baker plan has not been thoroughly worked out, but bankers and Latin American officials said they understand that many of the new loans to the debtor nations would be made only if debtor nations agree to take economic reforms that eliminate inefficiencies and remove roadblocks to growth.

But many powerful interests in state enterprises believe they benefit from being owned or linked to the central government.

Workers fear, often with good reason, that they will be laid off if their enterprises are sold to private interests. Many of the enterprises owned by the state were acquired to prevent them from failing. Managements have grown secure knowing that any losses are covered by central budgets.

Even privately owned companies often are protected from outside competition. With the exception of Brazil, most debtor nations have small internal markets, and their protected private sectors often are inefficient, produce inferior goods or both.

Mexican officials say privately that the private sector is as big an impediment to economic reform as the public sector.

In Brazil, an attempt to eliminate several small government companies full of documented inefficiency and payroll padding met with strong resistance.

The kinds of structural adjustments that apparently would be required under the Baker proposal may promise the benefits of economic growth, but also may be more difficult to carry off than the adjustments required by the IMF, even though the IMF reforms promised serious recessions.

As a result, officials caution, it may be some months before the initial loans are made to countries under the Baker proposal -- even if the banks and the development institutions agree on exactly how and under what terms they will cooperate in the plan.

Because the Baker plan apparently stipulates that loans be made only to countries that are in compliance with IMF programs or are taking steps that are approved by the IMF, eyes have turned to Argentina as the likely candidate for a pilot loan under the initiative. It is the only major debtor that is in compliance with the IMF and eligible for World Bank loans.

Mexico and Brazil, the two biggest debtors, are out of compliance with IMF programs they agreed to nearly three years ago. Peru has no program and refuses to deal with the multilateral organization.

Assistant Treasury Secretary David Mulford has been to Argentina. Federal Reserve Board Chairman Paul A. Volcker will visit Buenos Aires this week.

But Argentine Finance Minister Juan V. Sourrouille said last week that the nation, which has about $50 billion in foreign debts, is not ready to jump headlong into the Baker initiative