WASHINGTON - The United States must dig deeper into its pockets to feed the world's hungry, the head of the World Food Program said on Tuesday, urging the world's top provider of food assistance to increase aid budgets.

Josette Sheeran, executive director of the Rome-based organization, underlined at an oversight hearing in the U.S. House of Representatives the severity of need among the world's hungry and malnourished: each day, 25,000 people die from hunger or related illness, one child every five seconds.

While some victories have been scored in past decades, Sheeran sees ahead a "perfect storm of challenges" - a changing climate and increasing droughts and floods, the scourge of HIV/AIDS, a boom in commodity prices, and slipping levels of food aid that have dropped to their lowest volume in 15 years.

With officials here scrambling to stretch aid budgets and cope with growing crises abroad, debate is raging this year in Washington over how best to deliver U.S. assistance.

The House has already passed a bill that would tweak U.S. food aid policy as part of the 2007 farm bill, which sets agriculture, food aid, and nutrition law for the next five years. The Senate is now working on its version.

In recent months, lawmakers have clucked about inefficiency and waste in a system that, however well-intentioned, spends 65 percent of emergency funds on overheads, and often delivers aid woefully slow. But it's unclear what real steps toward change the final law will take.

The House has appropriated $1.2 billion for emergency food aid in fiscal 2008, slightly more than the previous year.

But in five of the last six years, Congress has approved last-minute, supplemental funds to cope with pressing crises, putting total spending in recent years around $2 billion.

Sheeran said she is "gravely concerned" this year will bring the same. She thanked lawmakers for "absolutely vital" U.S. generosity, but urged them to increase up-front emergency funding to at least $2.5 billion.

Another point of contention this year has been a Bush administration proposal to allow up to a quarter of emergency food aid money to be spent on crops abroad, sidestepping high transport costs and lengthy delays that can come with buying U.S. crops. The proposal has pitted shippers and farm groups against would-be reformers and has divided the aid community, but it has gotten little traction in Congress.

The WFP backs giving aid in cash, but it wants to see that come on top of existing aid levels.

"With a growing population, the absolute number of hungry people just keeps rising," now at about 850 million people, Sheeran, a former high-ranking State Department official, told an appropriations subcommittee on agriculture.

Sheeran objects to a measure in the House bill -- similarly expected in the Senate -- that would set aside a portion of emergency aid to fund longer-term development projects, like teaching better farming techniques or improving nutrition.

The set-aside is popular among charities that receive U.S. commodity donations and sell them abroad to finance their development work. But they're a target for reformers who believe they pull money away from pressing needs and can make things even worse by distorting markets in poor nations.

"This measure could have a severe impact on the people who need our help the most," she said. Again, WFP would like to see the longer-term funding on top of existing emergency aid.