The European Commission has condemned Russia's decision to suspend meat imports from the EU as unnecessary and unjustified.
Russia stopped the imports from up to half of EU countries, including France, Germany, Poland and the Czech Republic, in a row over veterinary certificates.
A spokesman said the commission was surprised by the Russian decision which, he said, was not the kind of behaviour one would expect from a potential World Trade Organisation (WTO) member.
Up to 12 EU countries could be affected by the ban
Reijo Kemppinen, chief spokesman for the EU executive, said that the measures could potentially affect 1.3bn euros (£864m) in trade annually.
"Any disruption of trade is unnecessary and unjustified. These measures do not correspond to any scientific assessment of the risk, nor are they backed up by appropriate risk management measures," he said.
"EU exports are safe and they are healthy. We insist that, in line with the recent agreements between Russia and the European Union, these restrictions are given up and difficulties overcome immediately."
Last month, at a bilateral summit in Moscow, the EU said it supported Russia's membership of the WTO, after Moscow had reluctantly agreed to extend its co-operation agreement with the EU to the 10 new countries that joined on 1 May.
Eight of the new members belonged to the former Soviet bloc.
Mr Kemppinen declined to speculate what counter-measures the EU could take, but said that Russia's behaviour was not one expected from a potential WTO member.
Russia has asked for a over a year that the EU should introduce a single veterinary certificate to replace the individual certificates currently issued by the 25 EU countries.
While technical discussions with Russian officials on the certification are still ongoing, the EU insists it has no legal basis to issue the single document requested by Moscow.
On the other hand, all EU countries are supposed to follow the same principles for the veterinary paperwork and Russia is entitled to send veterinary inspectors abroad, just like the EU.
Some of the new EU members see the move as another Russian manoeuvre to intimidate them.
But Mr Kemppinen said it had nothing to do with the EU's eastward expansion.
"This is not a new member state issue," he said.
He said the Russian measures appeared to be selective, but the precise information as to the products covered by these restrictions were not yet clear.
However he said they would have an impact on 11 or 12 member states: the Netherlands, Germany, Poland, the Czech Republic, Latvia, Estonia, France, Belgium, Denmark, Ireland, Austria and possibly Finland as well.
"We simply cannot imagine that Russian authorities want to take such extraordinarily unfriendly action - all 148 members of the WTO accept our export certificates," he said.
Mr Kemppinen said the reason for the action was difficult to understand.
But other EU officials believe it is linked to a protectionist sentiment in the Russian agriculture ministry.
They compare the move to a similar ban imposed last year on US chicken imports, when the Russian chicken industry was going through difficulties. But they also point out that Russia cannot afford to alienate for long its biggest trade partner.
The EU accounts for over half of Russia's trade - providing almost 80% of its beef imports and half of its pork imports.