U.S. corn prices have surged more than 55 percent in five weeks as crops continued to wilt under the worst drought in the U.S. Midwest since 1956, stoking fears of food shortages, and little respite on prices is in prospect.

Abdolreza Abbassian, senior economist and grain expert at the UN's Food and Agriculture Organisation (FAO) said plentiful supplies of rice and better availability of wheat meant the situation was not as serious as four to five years ago.

A mix of high oil and fuel prices, growing use of biofuels, bad weather and soaring grain futures markets pushed up prices of food in 2007/08, sparking violent protests in countries including Egypt, Cameroon and Haiti.

"It is a serious situation which has to be monitored closely but it is too early to refer to it as a food crisis situation," he said. "We do not see any production or supply problems with rice. That is very important for food security of millions of people around the world."

Record high prices for staple foods last year were a major factor contributing to the Arab Spring uprisings in the Middle East and North Africa, as well as bread riots in other parts of the world.

CAUSE FOR CONCERN

"We are concerned for two reasons," Abbassian said.

"First, the pace at which price rises are taking place and second, because at least for the time being there seem to be no relief in prices, in particular for corn, soybeans and wheat," Abbassian told Reuters in a telephone interview.

Export prices of corn (maize) and wheat jumped some 20 percent in the first three weeks of July compared to their June level, the FAO said it its price update on Friday.

That is likely to lead to a rebound in international food prices in July after three months of falls, Abbassian said. The FAO is due to update its international food price index on August 9.

The current surge in grain prices, coupled with strong U.S. dollar and economic slowdown in many Western countries which saps consumer demand, is likely to deal a heavy blow to developing countries many of which import grains and export other commodities.

"The combination of a higher import bill and lower export earnings will be an additional stress for their economies. That could create difficult and for some countries unpredictable situations," Abbassian said.

The FAO expected world coarse grain supplies to tighten in the current season due to corn problems in the drought-stricken United States. The U.S. Deportment of Agriculture (USDA) is expected to cut its view of corn yields in its upcoming updates, Abbassian said.

(Reporting by Svetlana Kovalyova; editing by Keiron Henderson)

By Svetlana Kovalyova