The World Bank will increase its yearly loans nearly 50 percent by 1992 to help end poverty in the Third World, the organization's president said today. Barber B. Conable spoke in West Berlin during the annual meeting of the bank and its sister organization, the International Monetary Fund. Participants from 151 nations have spent a week exploring ways to lighten the debt load of poor nations. The meeting ends today. Leftist groups have mounted protests to criticize the international banks, which make development loans, for insisting on repayment by Third World nations. About 1,000 demonstrators gathered at a church nearby Wednesday and chanted ``IMF Murder Meeting.'' Thousands of riot police held them back with plastic shields. Third World countries owe about $1.2 trillion to international and private lenders as well as governments. Conable predicted that the World Bank will be lending $25 billion dollars a year by 1992 to Third World nations. It now lends about $17 billion a year, and the monetary fund provides about $8 million more. Speaking at a news conference, he said $5 billion will go to the poorest countries, which are mainly in Africa. Conable said the bank will strengthen its aid by sharing more financing with other donors. He said Japanese officials have told him they plan to help and promised to talk with him about a program. Contributions to the bank come from the 151 member governments. Conable also pinpointed trade imbalances as part of the debt problem faced by poor countries. He said they cause losses twice as great as the aid such countries receive from wealthier nations. Speakers from the Third World have protested repeatedly at the meeting that the industrial countries put up barriers to their exports that prevent debtor countries from earning money. In an interview before his news conference, Conable said he believed interest rates were stabilizing after recent increases. The financial leaders have listened this week to warnings that higher interest rates, used by the United States and other industrial countries to cool inflation, threaten the Third World. ``It would be highly undesirable if an excessive concern for inflation were to bring about a spiral of interest rate rises,'' said Giuliano Amato, Italy's treasury minister. At Wednesday's sessions, participants seeking new ways to ease the burden of debt heard about the cost of higher interest rates to Third World countries. Every 1 percent rise in interest rates costs the debtors $6 billion more a year, said Stanley Fischer, vice president and chief economist of the World Bank. The United States and other industrial countries view higher interest as a way of controlling price increases. In the United States, higher interest rates also attract money from abroad to meet the federal budget deficit. Third World countries pay more than $50 billion a year on loans subject to variable interest rates. They complain that too much of their earnings go to pay interest, leaving little to improve living standards. In many of them, especially in sub-Saharan Africa, people's incomes have been declining for 20 years.