The food crisis is said to have pushed 100 million people into hunger
The United Nations food summit in Rome is struggling to reach agreement on its final declaration as Argentina objects to a call to reduce trade barriers.
A member of the Argentine delegation said it wished to achieve consensus but added that "the trade language [was] very controversial".
Other areas of disagreement are said to be Cuba and biofuel cultivation.
Delegates had been due to issue a declaration on "eliminating hunger and securing food for all".
It had been expected at 1500 local time (1300 GMT) on Thursday.
Sue Kedgley, a Green MP and member of the New Zealand delegation, confirmed that Latin American countries were behind the delay in agreeing a final statement.
"The discussions have been going on day and night," she told the BBC.
"The declaration seems to be bogged down. Argentina wants the ability to impose its own trade restrictions and the document doesn't say that."
Export taxes have been a controversial issue in Argentina where they are used to protect consumers against food inflation.
Disagreement also arose between opponents and supporters of communist Cuba about mention of US sanctions.
US Agriculture Minister Ed Schafer said no agreement on the declaration was better than "bad" agreement.
"We see a lot of talk about donations, about money being put on the table, about an effort to feed people who are hungry and in need and that's a good outcome," he added.
The summit was called by the UN's Food and Agriculture Organisation to seek ways to secure food supplies in the face of rising demand - especially from rapidly developing Asian countries - poor harvests and rising fuel costs.
The Organisation for Economic Cooperation and Development sees prices of rice, corn and wheat retreating from peaks but still up to 50% higher in the next decade.
The FAO says food production must rise 50% by 2050 to meet demand.
Momar Ndao, a Senegalese campaigner who took part in price riots in March, said that if no action was seen to be taken, there would be more riots fuelled by anger over the cost of living in impoverished western Africa.
Aid experts say soaring global prices for foodstuffs and fuel threaten to push 100 million people worldwide into hunger, and governments in the poorest countries are scrambling to find ways to mitigate the effects.
Earlier, senior European officials said some countries were refusing to sign a final statement "demonising" biofuels.
But Brazilian officials denied that biofuels were the sticking-point, instead blaming "commercial and agricultural points".
Brazil has fiercely defended its right to grow sugarcane for ethanol.
The summit wants urgent action to help farmers plant more crops this year, but there are disagreements over the role of biofuels in driving up food costs.
The World Food Programme has also said it will try to source most of its food from developing countries.
Some £3bn (£1.5bn; £2bn euros) of new aid was pledged during the summit to help ease the food crisis.
And on Wednesday, the World Food Programme announced an extra $1.2bn in assistance for 60 of the hardest hit nations.
But the big sums needed will not be announced until later in the year.
Jacques Diouf, the head of the UN's Food and Agriculture Organisation (FAO), which is hosting the summit, said investment in seeds was essential in the next few weeks to take the maximum opportunity from this year's harvest.