MOSCOW: Russia, one of the world's largest wheat exporters, is considering a formula-based tax on the wheat it sends abroad from June 1, a month earlier than previously stated, two sources familiar with government talks told Reuters on Saturday.

Moscow is attempting to reduce wheat exports to help curb rising domestic food prices after President Vladimir Putin criticised food inflation amid the coronavirus pandemic.

It has already said it would impose fixed tariffs - set at 25 euros ($30) per tonne for Feb. 15 to 28, rising to 50 euros per tonne from March 1 to June 30 - on wheat exports, but this was just a short-term measure and it has said it planned to switch to a more complicated formula-based regime on July 1.

Sources said the formula may be set at 70% of the difference between the price of wheat per tonne and $200, starting from June 1, though one added that officials are still debating what to set as the price for the formula.

Russia's agriculture ministry did not reply to a Reuters request for comment. The economy ministry said it and other ministries were working on "various options to ensure that the President's task of curbing the rise in food prices is fulfilled".

The final decision on the formula-based wheat export tax is likely to be ready next week, sources said.

Russian wheat with 12.5% protein loading from Black Sea ports for supply before mid-February was at $296 a tonne free on board (FOB) at the end of last week, according to the IKAR agriculture consultancy.