A summit between Russian President Vladimir Putin and his Turkish counterpart, Recep Tayyip Erdogan, has failed to bring Russia back into an agreement that had allowed Ukrainian grain exports via the Black Sea.

After the talks on Monday in the southern Russian city of Sochi, Putin told reporters that Moscow will be ready to consider reviving the deal, but only if all agreements on lifting curbs on Russian farm exports are implemented.

Erdogan said work must continue to be done to narrow the gaps. He added that he believes a solution can be reached in a short period of time, based on new proposals put forth by his government and the United Nations.

He also said Ukraine needs to soften its approaches in order for it to be possible for joint steps to be taken with Russia.

Ukraine is one of the world's top grain exporters. The latest failure to revive the grain deal could lead to concerns over a possible food crisis.