Russia says that two major Ukrainian ports on the Sea of Azov seized by Russian forces were ready to resume grain shipments, but the Kremlin said Kyiv still needed to demine the approaches to its ports for exports to take place.
Russia has seized large parts of Ukraine's coast in nearly 15 weeks of war and its warships control the Black and Azov Seas, blocking Ukraine's farm exports and driving up the price of grain.
Ukraine and the West accuse Moscow of weaponising food supplies. Russia blames the situation on what it says are Ukrainian mines, and on international sanctions against its own economy.
Defence Minister Sergei Shoigu said the ports of Berdyansk and Mariupol, the latter city destroyed after a three-month Russian siege, had resumed their operations.
"The de-mining of Mariupol's port has been completed. It is functioning normally, and has received its first cargo ships," Shoigu said in televised comments.
The Sea of Azov is shallower than the Black Sea and its ports are only accessible to smaller vessels. Ukraine's main port of Odesa remains blocked.
More than 20 million tonnes of grain are stuck in Ukraine awaiting shipment, and Ukrainian President Volodymyr Zelenskiy said this could rise to 75 million by the autumn.
Kremlin spokesman Dmitry Peskov told reporters Ukraine still needed to demine its coast for grain exports to take place.
"This will allow ships, once checked by our military to make sure they are not carrying any weapons, to enter the ports, load grain and with our help, proceed to international waters," he said.
Ukraine has accused Russia of stealing vital grain supplies - claims U.S. Secretary of State Antony Blinken has called "credible" - while Moscow says Western sanctions are to blame for the situation, which has threatened to trigger a global food crisis. read more
The United Nations is working on plans with Kyiv and Moscow for how to restart grain exports from Ukrainian ports, with Turkey possibly set to provide naval escorts to ensure safe passage out of the Black Sea. read more
Russian Foreign Minister Sergei Lavrov will visit Turkey on Wednesday to discuss the proposals.
Shoigu also said Russian forces had restored railway traffic across southern and eastern Ukraine and started delivering cargo to Mariupol, Berdyansk and Kherson on 1,200 km (750 miles) of reopened tracks.
Creating a so-called "land corridor" between Russia and the Crimean peninsula, annexed by Moscow in 2014, has been a major part of Russia's strategy since the start of its offensive.