A Treasury official said today that new U.S. proposals for dealing with the debt crisis probably will prod the World Bank to channel more funds to debtor nations this year.

Assistant Treasury Secretary David Mulford said the World Bank "has about $2 billion available this year that they are not lending." The proposals made Tuesday by Treasury Secretary James A. Baker III will persuade the bank to get that money into debtor nations' hands, he said.

Mulford said in an interview that "we have a tremendous influence on the bank management, and they want to move this way as well."

Baker called for new loans by international lending agencies as well as commercial banks, and for actions by debtor countries to improve their economies and open their markets. Mulford said that action within the next several weeks is necessary to implement the program.

Mulford said that in addition to pushing the World Bank, the Reagan administration wants to make Inter-American Development Bank operations more efficient. A large refunding of the IDB is scheduled early next year. "We will not be willing to join in the replenishment for the IDB unless economic reforms can be carried out by the principal debtor countries in Latin America that the IDB serves," Mulford said.

Baker's goal is to boost the multilateral development bank loans -- by the World Bank and other agencies -- by $9 billion over the next three years, an increase of 50 percent over current projections.

Mulford said that it is critical that this increased lending activity by the international organizations take place if the Baker plan is to succeed in getting additional commercial bank loan commitments of $20 billion over the next three years for middle-income debtor countries.

Mulford acknowledged that the new program amounts to a major shift in U.S. thinking, and demonstrates "a willingness on the part of the United States to take more of a leadership role" in the management of the debt crisis.

"It's been our view for a long time that the World Bank has not been using its resources effectively," Mulford said. He would not comment on whether this view played a part in the decision of World Bank President A. W. Clausen not to seek appointment for a seond term. But other sources left no doubt that the administration had lost confidence in Clausen and decided that the bank needed a more dynamic leader.

Mulford said that "a perfect example" of a more aggressive lending policy by the bank would be a large, quick-disbursing structural adjustment loan for Argentina that would help its economic recovery.

He also complained that the bank is slow to move and make decisions, compared with the speed of the International Monetary Fund. "They can streamline things," Mulford said of the World Bank.

Mulford said that the bank had worked at cross-purposes with the IMF, citing a case where the bank had gone ahead with a $140 million agricultural loan for the Philippines "at a time when that economy was in a shambles" and the IMF was trying to restore it with an across-the-board program. "They the bank should have had a greater sensitivity," he said.

He acknowledged that the commercial banks will be willing to make increased loan commitments only if the multilateral banks are lending more money.

He added that the "three-legged stool," as Baker referred to his program, also requires that the borrowing countries take steps to stimulate their own economic growth and to halt the flight of domestic capital out of their countries.

Mulford said that it is now up to the major international commercial banks to get together to plan how to share the increased loan amounts. He said that the Treasury looks to a group of about 100 to 150 of the world's largest banks to lead the way, encouraging smaller banks "to stay in the picture, even if they don't enlarge their commitments.

"Once the concept is understood, they will see that they have everything to gain and nothing to lose. If the debtor countries commit themselves to readjustment, the banks will be the gainers."

Asked if the commercial bankers wouldn't be encouraged if the Reagan administration backed a general capital increase for the World Bank, Mulford said it would be wrong to expand the agency's lending resources "at a time when they don't really need it." Besides, Mulford said, if a capital increase were approved now, it would reduce the incentive of the commercial banks to boost their loans by the requested $20 billion. CAPTION: Picture, David Mulford . . . says bank has $2 billion to lend.