The United States will urge other countries to boost food supplies by lifting restrictions on bio-engineering technologies to drive down costs and alleviate the global crisis in food shortages, a top US official said Thursday, dpa reported.

US Agriculture Secretary Ed Schafer said he will press developed nations to become more efficient in producing food to combat the rising price of food at a UN conference in Rome June 3-5 to address the shortages in poorer countries.

"The United States contributes more than one-half of all the world's food aid, and the world's other developed nations have an obligation to provide food efficiently, without obstructing access to it or limiting safe technologies to produce it," Schafer told reporters.

Some European and African countries are sceptical about the safety of bio-engineered or genetically modified foods.

Schafer said he will also try to dampen the argument that bio- fuel production has been the main source of the spike in food costs. He said a Department of Agriculture analysis concluded that the shift in recent years by farmers to produce bio-fuels instead of food crops has only accounted for a 2-3 per cent rise in food costs.

"Bio-fuels are just one contributor to increased food prices, as demonstrated by price increases on all commodities, both food and nonfood," Schafer said.

Some developing countries have called for an end to subsidies for bio-fuels derived from food crops such as maize. The World Bank has said US production of maize-based ethanol is the chief cause of a spike in maize prices over the last few years.

Schafer said ethanol production was spurred by an increased yield from US maize crops and was not pulling resources out of "traditional markets."

He said the increase in food prices can be largely blamed on record-high energy prices that have also prompted a rise in food transportation costs. Bio-fuels help cut down on the dependence on oil and greater production of bio-fuels would ease the crunch in producing and shipping food.

"This is not distorting the global price of food and it's an important direction we need to go," Schafer said.

Schafer said the United States has focused on humanitarian assistances to countries unable to meet minimum nutritional standards and will urge countries at the conference to expand research into innovative technology to produce food, including biotechnology.

"Some basic examples of this are encouraging a policy environment that invests in water management, fertilizer and seed marketing, agriculture credit, and improved post-harvest management," he said.

More than 40 heads of state are expected to attend the UN conference.