The secretary-general told the Rome summit that nations must minimize export restrictions and import tariffs during the food price crisis and quickly resolve world trade talks.
"The world needs to produce more food," Ban said.
The Rome-based U.N. Food and Agriculture Organization is hosting the three-day summit to try to solve the short-term emergency of increased hunger caused by soaring prices and to help poor countries grow enough food to feed their own.
In a message read to the delegates, Pope Benedict XVI said "hunger and malnutrition are unacceptable in a world which, in reality, has sufficient production levels, the resources and the know-how to put an end to these tragedies and their consequences."
The Pope told the world leaders that millions of people at threat in countries with security concerns were looking to them for solutions.
Ban said a U.N. task force he set up to deal with the crisis is recommending the nations "improve vulnerable people's access to food and take immediate steps to increase food availability in their communities."
That means increasing food aid, supplying small farmers with seed and fertilizer in time for this year's planting seasons, and reducing trade restrictions to help the free flow of agricultural goods.
"Some countries have taken action by limiting exports or by imposing price controls," Ban said. "They only distort markets and force prices even higher."
The increasing diversion of food and animal feed to produce biofuel, and sharply higher fuel costs have also helped to shoot prices upward, experts say.
The United Nations is encouraging summit participants to start undoing a decades-long legacy of agricultural and trade policies that many blame for the failure of small farmers in poor countries to feed their own people.
Wealthy nations' subsidizing their own farmers makes it harder for small farmers in poor countries to compete in global markets, critics of such subsidies say. Jim Butler, the FAO's deputy director-general, said in an interview ahead of the gathering that a draft document that could be the basis for a final summit declaration doesn't promise to overhaul subsidy policy.
Congress last month passed a five-year farm bill heavy on subsidies, bucking White House objections that such aid in the middle of a global food crisis wasn't warranted.
The head of the summit's U.S. delegation, Agriculture Secretary Ed Schafer, insisted on Monday that biofuels will contribute only 2 or 3 percent to a predicted 43 percent rise in prices this year.
[to top of second column]
Figures by other international organizations, including the International Monetary Fund, show that the increased demand for biofuels is contributing by 15-30 percent to food price increases, said Frederic Mousseau, a policy adviser at Oxfam, a British aid group.
"Food stocks are at their lowest in 25 years, so the market is very vulnerable to any policy changes" such as U.S. or European Union subsidizing biofuels or mandating greater use of this energy source, Mousseau said.
Brazil is another large exporter of biofuels, and President Luiz Ignacio Lula da Silva was expected to defend biofuels at the summit.
Several participants won't even be talking to each other at the summit.
Australia's foreign minister decried as "obscene" Zimbabwean President Robert Mugabe's participation in the summit. The longtime African leader has presided over the virtual transformation of his country from former breadbasket to agricultural basket case.
Zimbabweans increasingly are unable to afford food and other essentials with agriculture paralyzed by land reform and the world's highest rate of inflation.
The Dutch ministry for overseas development pledged to "ignore" Mugabe during the summit.
EU sanctions against Mugabe because of Zimbabwe's poor human rights record forbid him from setting foot in the bloc's 27 nations, but those restrictions don't apply to U.N. forums.
Jewish leaders and some Italian politicians were among those denouncing Iranian President Mahmoud Ahmadinejad's attendance at the meeting. On Monday, Ahmadinejad repeated his call for the destruction of Israel, which is also participating in the summit.
Ahmadinejad was scheduled to give a summit news conference Tuesday afternoon.
Schafer, asked about the presence of the Zimbabwean and Iranian leaders, told reporters in Rome that the two were welcome to attend the summit, but that U.S. delegates would not be meeting with them.
[Associated Press; By FRANCES D'EMILIO and ARIEL DAVID]
Copyright 2008 The Associated Press. All rights reserved. This
material may not be published, broadcast, rewritten or