Treasury Secretary James A. Baker's proposals for a shift in strategy for dealing with the Third World debt crisis received a mixed reaction from the international financial community today.

In his address to the joint annual meeting of the World Bank and the International Monetary Fund, Baker called for a program emphasizing economic growth in the Third World, fed by fresh cash from commercial banks and the multilateral development banks, including the World Bank.

As Baker departed for Washington immediately after his speech, officials said they welcomed any initiative in the face of a new and apparently more serious phase of the debt crisis.

"The international economic system has reached the point of no return," IMF Managing Director Jacques de Larosiere said in his annual address. "There is no alternative to closer cooperation and leadership. It is now up to the international community to act, and to act together."

De Larosiere reported that export earnings of the developing nations are expected to shrink 2.5 percent this year after rising 8 percent in 1984, compounding their cash-flow problems.

What happens now to Baker's proposals is problematical. There will be no action taken at the IMFWorld Bank annual meeting. But his ideas no doubt will be raised in private conversations with bankers and managers of the multinational lending agencies expected to provide new funding.

Discussions also could be held with officials of debtor countries being asked to modify their economic policies and welcome foreign investment.

But there was widespread skepticism that Baker had offered a meaningful solution to the debt problem.

"It is clear to me that the United States, like some other countries, wants to promote and expand the role of the World Bank," said H. Onno Ruding, chairman of the influential IMF Interim Committee. "But it is not clear how this is to be implemented without a general capital increase for the bank."

Baker said the bank has enough resources to expand its lending without a general capital increase, but didn't rule one out if demand for "quality" lending increases.

Ironically, the new focus on the World Bank came on the day that its president, A. W. Clausen, announced that he will retire next June when he completes a five-year term.

Bankers and other officials also were skeptical that the "commitment" Baker had said he would seek from commercial banks for $20 billion in fresh lending to some 15 middle-income countries over three years would materialize.

A senior administration official who remained in Seoul after Baker left said at a briefing tonight that the Treasury secretary had received "a favorable reaction" from American banks that had been given advance information on the program last week in Washington.

He said that the posture of European banks was less clear, but "it seems to me that these American banks have every reason to continue to lend. They are heavily lent now, and eventually they will have to face this situation. It seems to us they would rather have this three-legged approach. So the banks have every reason to be positive."

John McGillicuddy, chairman of Manufacturers Hanover Trust Co., called the Baker proposal the "first plan that is prospective rather than reactive to the problems," and said his bank, one the biggest lenders to Latin America, supports it and will "work with others in further developing the plan."

Nonetheless, many private commercial bankers who circulate at these annual meetings indicated they wondered whether Baker had not oversold the potential of a debt rescue operation making demands of a commercial banking system already overcommitted in the Third World.

A Latin American banker said the three major debtor countries in his area now have an annual interest burden of $25 billion, and need the foreign banks -- mostly American -- to refinance $10 billion of that amount. But if that money is provided on lenient terms, "that will cut into the profits of your banks," he noted.

Robert Hormats, a former government official and now a vice president of the investment banking firm of Goldman Sachs & Co., said, "Without the enormous buildup, Baker's proposals might have been viewed as a reasonable first step."

A Treasury official expressed regret that Baker had to withdraw a proposal to create a pool of $5.4 billion for sub-Saharan countries and other poor nations through a unified World Bank/IMF operation. He revealed that the United States had been prepared to make a contribution on its own to this pool, supplementing bank and IMF money.

In his speech to the annual meeting, Baker said, "I would like to see the banking community make a pledge to provide $20 billion in new lending and make it publicly, provided the debtor countries also make similar growth-oriented policy commitments as their part of the cooperative effort."

But neither Baker nor the senior Treasury official who briefed reporters later could say who would make these pledges on behalf of the bankers or debtors.

Ruding of the IMF interim panel, who is also finance minister of the Netherlands, said: "You can't summon the bankers, and say, 'Do this or that.' " He argued that the logic of Baker's case -- that the debt crisis had worsened, calling for greater World Bank loans -- "requires a commitment right now for a general capital increase."

Actually, Baker was more forthcoming on the possibility of U.S. approval of a general capital increase for the World Bank than he had been before coming to Seoul. Moreover, he hinted there could be support later for a similar increase for the Inter-American Development Bank.

It was this new suggestion of greater cooperation with the multilateral development banks sprinkled through Baker's speech that encouraged representatives of the developing nations. They saw a new willingness by the U.S. administration not only to take a hand in managing the debt crisis, but also to expand the role of the international lending banks. At the start of the Reagan administration, the policy was the reverse.

Observers here suggested that further rapport between the Reagan administration and the World Bank could develop once the White House settles on its choice to succeed Clausen as the bank's president.

Among those prominently mentioned as candidates are Federal Reserve Board Chairman Paul A. Volcker, former Citicorp chairman Walter Wriston, and Deputy Secretary of State John Whitehead.