A k e y UN-sponsored summit has opened in Rome aimed at addressing the problem of soaring global food prices.
Food costs are the highest in 30 years, causing riots in dozens of countries.
Secretary General Ban Ki-moon said the world had a "historic opportunity to revitalise agriculture", and called for export restrictions to be minimised.
But many observers have so far focused on Zimbabwe's Robert Mugabe, whose presence at the summit has been called "obscene" by the UK and Australia.
Australian Foreign Minister Stephen Smith said the Zimbabwean president was "the person who has presided over the starvation of his people".
Biofuel issue The host of the Rome conference - the UN's Food and Agriculture Organisation (FAO) - has warned the industrialised countries that unless they increase yields, eliminate barriers and move food to where it is needed most, a global catastrophe could result.
The recent crisis is believed to have pushed 100 million people into hunger worldwide.
Poorer countries are faced with a 40% increase in their food imports bill this year, and experts say some countries' food bills have doubled in the past year.
"A lot of countries have to import more or less as what they did in the past, they had to because it's the basic food," FAO official Abby Abbassian told the BBC.
"But that means they must have spent at least twice as much as in the previous year because prices have gone up at least by 100%."
The BBC's Christian Fraser in Rome says the FAO is calling on donor countries to dig deeper - to help farmers in developing countries get access to fertiliser, seeds and the animal feed they require.
It says the problem of chronic underinvestment in agriculture can no longer be ignored.
Ahead of the conference, the Islamic Development Bank said at a meeting in Saudi Arabia that it would spend $1.5bn (£760m) over five years to help the least developed Muslim countries tackle the food crisis.
One area expected to generate disagreements in Rome is biofuel - most of the increase in maize production last year went into making fuels such as ethanol, not food.
Mr Ban intends to ask the US and other countries to phase out subsidies that encourage farmers to produce for fuel.
UN officials said there would be a range of "confidence-building" options for governments.
The taskforce Mr Ban created to target the food crisis is expected to present a 38-page report with measures that could cost up to $15bn (£7.5bn) to implement. In the short term, the report will call for a reduction in tariffs and the provision of subsidies for poorer farmers.
Long-term measures will focus on increased investment.
On the eve of the summit, Mr Ban said "we are literally paying the price" for overlooking investment in agriculture.
"If not handled properly, this issue could trigger a cascade of other crises - affecting economic growth, social progress, and even political security around the world," he warned.
The main causes of the rising food prices include rising demand from fast-developing countries, higher oil costs and global warming.