Secretary of State Cyrus Vance warned last night that the world energy situation "is likely to get worse before it gets better," with demand continuing to outpace increases in supplies.

Vance's gloomy perspective on the oil problem came in a speech on economic development problems in the poor nations, prepared for delivery at the Northwest Regional Conference in Seattle.

He said that as a consequence of the more serious energy problem, the United States would be responsive to additional efforts to expand oil production in the developing countries, including greater flows of private capital from the rich nations.

Vance mentioned that the World Bank, with the "strong support" of the United States, already plans loans of up to $3 billion over the next five years for new development of fossil fuels in the developing countries. He implied this amount could be boosted.

Amony other specific new steps, Vance revealed that the economic summit in Tokyo June 28-29 among President Carter and six other heads of state would accelerate a plan to harness "the vast energy potential of the sun, wind, the oceans and other renewable resources." This plan was initiated last June at the Bonn economic summit.

The secretary said that these and other efforts to expand the supply of energy are crucial to economic growth, for "there is no promise for any of us in an intensifying competition for limited energy supplies."

In addition to energy, Vance said that the United States intends to place a high priority on expanding the availability of food in the developing world. The newly appointed presidential Commission on World Hunger, he said, would make concrete proposals in this area this summer.

In a more general review of the U.S. strategy towards improving the "North-South dialogue" - the debate and negotiations between the rich and poor nations on increased aid - Vance appealed to the poor nations to shun unreasonable demands.

"In a period of fiscal austerity, there is a danger, which we must frankly address, that negotiations between the North and South could return to the rancor of earlier years," he said.

Progress, he suggested, will depend "on our common ability to avoid endless debates on sterile texts, and to focus instead on concrete development problems which we can tackle together, and which directly affect people's lives."

The United States stands by its commitment to increase the transfer of resources from the richer to poorer nations, Vance said, but warned that such transfer, or "alterations in the international system," are not ends in themselves.

Instead, Vance said, the United States gives first priority to programs that will not simply help poor countries grow, but which contribute to "equity" by inproving the lives of "poorer people abroad."