Russia's ban on food imports from the likes of the European Union and the US may lift domestic prices, but could raise food inventories in exporting countries, the United Nations said.
Abdolreza Abbassian, senior economist at the UN Food and Agriculture Organization, said that the "first casualties" of the Russia's curbs "would be the domestic market", with the country, a major importer of the likes of meat, fruit and dairy, likely to pay more to meet its needs from other origins.
However, the ban "will have some implications for farmers in the producing countries" too, Mr Abbassian said, flagging the potential, with Russian buyers absent, for a rise in inventories – a factor which might be expected to depress local prices.
The comments come as investors are attempting to gauge the impact on agricultural commodity markets of Russia's move on Wednesday to curb imports from some countries that have taken sanctions against Moscow over the Ukraine crisis.
The exact extent of the curbs is also unclear, although Aleksei Alekseenko, an aide to the regulator in charge of food inspections, said late on Wednesday that "everything [in the agricultural sector] that is produced and imported to Russia from the United States will be banned.
"Fruit and vegetables from the European Union will also be under a full ban."
Mr Abbassian told Reuters that "this is an exceptional situation where one cannot generalise on global food security" and that their impact on prices would be limited.
In the Chicago futures market, wheat – of which Russia and Ukraine are both major importers, and price of which prices have become a proxy for regional tensions – fell 0.7% to $5.64 ½ a bushel for September delivery, as of 05:30 local time (11:30 UK time).
Nonetheless, prices are up some 5% so far in August, having gained some ground ahead thanks to a rise in Russian troop movements at the border with Ukraine, even before the announcement of import curbs.
In the US, Brian Henry at broker Benson Quinn Commodities flagged market talk "of embargoing Russian wheat" as a response to Moscow's ban, although "I have strong doubts that a programme of this nature would find much participation".
With Russia a rich source of competitively priced wheat, a widespread ban its exports, even if workable, would have implications for food availability in importing countries.
Still, Mr Henry added that "this issue could escalate quickly, and this year's flow of grain will undoubtedly be different than last year considering quality problems and geopolitical issues".
Quality problems have emerged in the US, Ukraine and, in particular, the European Union thanks to harvest-time rains, which encourage kernel sprouting and reducing milling appeal – although Russia is one country where such issues do not seem widespread.
Nikolai Fyodorov, the Russian agriculture minister, said on Thursday that he expected the ban on food imports to have no effect on the country's grains exports, expected to hit 25m tonnes in 2014-15, he said, compared with 25.4m tonnes last season.
From a technical perspective, the rise in Chicago wheat prices has also been fuelled by a covering by hedge funds of short positions, with speculators having their second highest net short holding in futures and options combined as of Tuesday last week, the latest data available.
"The market has developed a large enough short position created this sort of action," Sterling Smith at Citigroup said, referring to a 3% bounce in prices on Wednesday.
From a chart perspective, Chicago futures in the last session did complete the retracement of 23.6% of their latest run down, a key point for followers of Fibonacci analysis.
"The 38.2% retracement level is at $6.07 a bushel," Mr Smith said.
"While do think this level is too far, political tensions of the type we are seeing can lead to irrational behaviour much like what we saw earlier this year."
Mr Abbassian was speaking after the UN FAO unveiled monthly world food price data showing a fall in values of 2.2% over July to a six-month low.
Cereals prices dropped 5.5% to a four-year low, "a reaction to excellent production prospects in many major producing countries and to the anticipation of abundant exportable supplies in the 2014-15 marketing season", the agency said.
Concepción Calpe, FAO senior economist, said that "the lingering decline of food prices since March reflects much better expectations over supplies in the current and forthcoming seasons, especially for cereals and oils, a situation that is expected to facilitate rebuilding of world stocks".
Dairy prices dropped 4.4%, thanks to confidence in supplies at a time when "purchases of butter by Islamic countries declined during Ramadan, as did those by the Russian Federation," the FAO said.
"For whole milk powder, limited purchases by China, the largest importer, contributed to a price drop."
Meat prices bucked the trend, edging 0.4% higher to their highest on records going back to January 1990.
"The increase was principally due to a strong rise of bovine meat prices in Australia, where herd rebuilding has reduced export supplies, and continued strong import demand in Asia, China in particular."
Ms Calpe said: "Livestock product markets have their own dynamics - in the case of meat, beef in particular, many exporting countries are in a herd rebuilding phase, which is limiting availability for exports and sustaining prices."