Russia said on Wednesday it has offered "safe passage" for Ukraine grain shipments from the country's Black Sea ports, but is not responsible for establishing the corridors, as Turkey suggested that ships could be guided around sea mines.
Ukrainian grain shipments have stalled since Russia's invasion and ports blockade, stoking global prices for grains, cooking oils, fuel and fertilizer.
The UN is trying to broker a deal to resume Ukraine grain exports and Russian food and fertilizer exports, which Moscow says are harmed by sanctions.
"We are not responsible for establishing safe corridors. We said we could provide safe passage if these corridors are established," Russia's UN Ambassador Vassily Nebenzia said.
"It's obvious it's either demine the territory, which was mined by the Ukrainians, or to ensure that the passage goes around those mines," he told reporters at the UN.
Turkish Foreign Minister Mevlut Cavusoglu said earlier on Wednesday that it would "take some time" to de-mine Ukraine's ports and a safe sea corridor could meanwhile be established in areas without mines under a UN proposal, adding that Ankara was still awaiting Moscow's reaction to the plan.
Kyiv fears that de-mining its ports would leave it far more vulnerable to Russian attack from the Black Sea.
"Since the location of the mines is known, certain safe lines would be established at three ports," Cavusoglu said. "These (commercial) ships, with the guidance of Ukraine's research and rescue vessels as envisaged in the plan, could thus come and go safely to ports without a need to clear the mines."
Cavusoglu discussed the plan with Russian Foreign Minister Sergei Lavrov in Ankara last week but said further discussions with Moscow and Kyiv were needed. Lavrov then said the onus was on Ukraine to clear mines around its ports for commercial ships to approach.
Moscow denies responsibility for the food crisis, blaming Western sanctions.
Turkey, which has the second-biggest army in NATO and a substantial navy, has good relations with both Kyiv and Moscow and has said it is ready to take up a role within an "observation mechanism" based in Istanbul if there is a deal.
Turkey's state broadcaster TRT Haber said a hotline had also been created between Turkey, Ukraine and Russia. Over the hotline a general from each country can take part in talks to "discuss the issue more closely and reach a result", it said.