Former West German Chancellor Willy Brant reported yesterday on the fourth meeting of an international commission that seeks ways to establish a more equitable relationship between rich and poor nations.

Brandt, head of the commission, said the four-day session at Tarrytown, N.Y., focused on problems of developing countries' debt, food and agriculture, migration of labor across national boundaries and trade.

The Independent Commission on International Development Issues, which held its first meeting last December, was organized after World Bank president Robert S. McNamara proposed that an indepedent body with members from the industrialized and developing worlds might be able to effectively address problems that have stymied other organizations.

Commission member Peter G. Peterson, who appeared with Brandt at a press conference here, said that one of the prime problems the commission faces is considering methods to create the political will in the rich nations to work toward eliminating present inequities.

Peterson said it was no secret that public opinion polls in the United States put a very low priority on aid for the developing nations. The commission aims to outline ways to overcome the existing apathy and ignorance in the rich nations, the former U.S. secretary of Commerce said.

As an example of the existing deep involvement of rich and poor, Peterson said the United States now exports more to the developing nations than to Europe and Japan combined.

Brandt said that peace is endangered not only by the arms race, but also by "the continuation of injustice amongst and within nations."

Brandt described himself as moderately optimistic that the commission will be able to write a report that produces results. He said the commission is well aware of the fate of most resports and does not intend its own to "simply end up on the bookshelves of experts." Brandt noted that former Canadian Prime Minister Lester Pearson delivered a report with closely related objectives in 1969.

If the commission's hopes are disappointed, Brandt said with a smile, "greater damage has been done to mankind" than publication of another report.

Brandt and commission staff members who appeared with him declained to be specific about the results of their Tarrytown discussion, which ended yesterday. The commission plans to deliver its report in mid 1979 and until then its recommendations will not be in final form.

Former Secretary of State Henry A. Kissinger, Sen. Jacob Javits (R-N.Y.) and International Monetary Fund Director Jacques De Larosiere were among those who spoke to the commission during the Tarrytown meeting.

Brandt announced that commission staff members made their first contact with the Soviet Union in July and planned to have further discussions. No members of the commission are from communist countries. He also said that former French Premier Pierre Mendes-France had resigned because of ill health, and his place has been taken by Sen. Edgard Pisani, a former French minister of agriculture.

The commission operates on an annual budget of $2.5 million from a headquarters in Geneva. It depends on contributions from governments and foundations, but operates independently of all governments and all other international organizations.

Its next meeting will be in Malaysia in November.