UN aid chief Martin Griffiths had "frank and constructive discussions" with Russian officials in Moscow on facilitating exports of Ukraine grain from Black Sea ports, a UN spokesman has said.
Mr Griffiths met with Russian foreign affairs and defence officials yesterday and today, UN spokesman Stephane Dujarric said.
Since Russia's 24 February invasion of Ukraine, Ukrainian grain shipments from its Black Sea ports have stalled and more than 20 million tonnes of grain are stuck in silos.
"We've said clearly what we can do and what we cannot do," Russian UN Ambassador Vassily Nebenzia told Reuters.
"We have not installed the mines in the coastal area, that was the Ukrainians. If they demine the area we are prepared to provide the safe passage for the ships carrying grain."
When asked if a security arrangement could be reached to allow for the demining, Ambassador Nebenzia said Russian Foreign Minister Sergei Lavrov planned to discuss the issue when he visits Turkey next week.
Today, Ukraine's ambassador to Ankara accused Russia of "stealing" and sending Ukrainian grain abroad to countries including Turkey.
"Russia shamelessly steals Ukrainian grain and sends it overseas from Crimea, including to Turkey," said Kyiv's envoy in Ankara, Vasyl Bodna.
"We have asked for Turkey's help to resolve the issue," he added in a message on Twitter.
UN Secretary-General Antonio Guterres is trying to broker what he calls a "package deal" to resume both Ukrainian food exports and Russian food and fertiliser exports.
Russia's war in Ukraine has fuelled a global food crisis with prices for grains, cooking oils, fuel and fertiliser soaring.
Russia and Ukraine account for nearly a third of global wheat supplies.
Russia is also a fertiliser exporter and Ukraine is a major exporter of corn and sunflower oil.
Mr Guterres also spoke with Belarus leader Alexander Lukashenko today.
The Belta news agency quoted Mr Lukashenko as telling Mr Guterres that Belarus is ready to allow the transit of Ukraine's grain to Baltic Sea ports via Belarus if it is allowed to ship Belarusian goods from these ports.
Meanwhile, Russia's President Vladimir Putin has said there is "no problem" in exporting grain from Ukraine amid fears of a global food crisis due to the ongoing conflict there.
He said it could be done via Ukrainian ports, via others under Russian control, or even via central Europe.
Mr Putin accused the West of "bluster" by claiming Moscow was preventing grain exports from Ukraine.
The Russian leader mentioned the possibility of exporting via the Ukrainian ports of Mariupol and Berdyansk on the Sea of Azov, which gives access to the Black Sea.
Both are under Russian control.
He also said ports under Kyiv's control, in particular, Odessa, could be used but called for the waters around the Ukrainian-held ports to be "cleared" of mines by Ukraine.
Russia would in exchange allow the ships safe passage, Mr Putin said.