Food prices are to remain high and volatile into 2012, presenting a "threat" to poor countries that will have to spend up to a third more on food imports this year, the UN food agency said on Tuesday.

The Rome-based Food and Agriculture Organisation (FAO) said its food price index averaged 232 points in May -- down from a revised estimate of 235 points in April but was still 37 percent above its level in May 2010.

"High and volatile agricultural commodity prices are likely to prevail for the rest of this year and into 2012," FAO said in a statement.

The reason for the monthly decline was the slight decrease in international prices of cereals and sugar, which offset increases for meat and dairy.

FAO said the next few months will be "critical" -- with encouraging prospects for the wheat harvests in Russia and Ukraine but a potential for lower maize and wheat yields in Europe and North America due to the weather.

"The general situation for agricultural crops and food commodities is tight with world prices at stubbornly high levels, posing a threat to many low-income food deficit countries," said David Hallam, head of FAO's markets division.

FAO said the cost of global food imports is set to reach a record of $1.29 trillion (879 billion euros) in 2011 -- 21 percent more than in 2010.

Low-income food deficit countries and least developed countries will likely have to spend 27 and 30 percent more respectively on food imports, FAO said.