The new money would come in addition to some $200m the US president released for emergency food aid two weeks ago, but Mr Bush warned that "more needs to be done".
"In some of the world's poorest nations, rising prices can mean the difference between getting a daily meal and going without food," he said.
"The American people are generous people and compassionate people. We believe in the timeless truth, to whom much is given, much is expected."
The new money is tied to a wider, $70bn spending measure that also covers funding for the wars in Iraq and Afghanistan in 2009.
The proposal has received broad approval, though some have criticised the fact that the funds will only be available in the next fiscal year.
Others highlight what they say are contradictions in the policies of President Bush's administration, which is simultaneously providing generous subsidies to US farmers to cultivate corn-based biofuels such as ethanol.
"It's a very good move, a very urgent move - but it doesn't solve the problem," Jean Ziegler, the UN special rapporteur on the right to food, told the BBC.
He says growing crops for fuel instead of food is one of the main causes of the price rises - but the White House counters that biofuel production accounts for only a small fraction of the recent food price increases.
Food price rises, dubbed by the United Nations World Food Programme (WFP) a "silent tsunami", have sparked riots in some countries, including Haiti, Cameroon and Indonesia.
Earlier this week, UN Secretary General Ban Ki-moon set up a task force to tackle the crisis.
George W Bush on food aid pledge
He said the priority was to feed the hungry by closing a $755m (£380m) funding gap for the WFP this year.
Mr Ban said the world faced "widespread hunger, malnutrition and social unrest on an unprecedented scale" because of soaring food prices, and urged donor countries to make more money available now.
The WFP believes 100 million people are currently going short of food.
It says only 62% of the $755m it needs to feed them has been pledged so far, and, of that, only $18m or 2.4% has actually been received.
Mr Ban said it was essential to support farmers in poor countries who were producing less because of the high cost of fertilizer and energy, and to this end he said the task force hoped to:
Offer $200m financial support to farmers in the worst affected countries to boost food production
Set up a $1.7bn programme to help countries with a food deficit to buy seeds
The task force, which Mr Ban will chair, will be made up of the heads of UN agencies and the World Bank.
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