* A solution to food problem requires vast approach - Moscow
* This includes lifting of some sanctions from Russia - Moscow
* Moscow is in touch with the UN on the issue
* Mariupol port is operating normally after demining - Moscow (Updates with comment from Ukrainian foreign minister)
May 25 (Reuters) - Russia is ready to provide a humanitarian corridor for vessels carrying food to leave Ukraine, in return for the lifting of some sanctions, the Interfax news agency cited Russian Deputy Foreign Minister Andrei Rudenko as saying on Wednesday.
Ukraine's Black Sea ports have been blocked since Russia sent thousands of troops into Ukraine on Feb. 24 and more than 20 million tonnes of grain are stuck in silos in the country.
Russia and Ukraine usually account for nearly a third of global wheat supplies and the lack of significant grain exports from Ukrainian ports is contributing to a growing global food crisis. Ukraine is also a major exporter of corn and sunflower oil.
Western powers have been discussing the idea of setting up "safe corridors" for grain exports from Ukraine's ports, although these would need Russian consent.
"We have repeatedly stated on this point that a solution to the food problem requires a comprehensive approach, including the lifting of sanctions that have been imposed on Russian exports and financial transactions," Rudenko was quoted as saying.
"And it also requires the demining by the Ukrainian side of all ports where ships are anchored. Russia is ready to provide the necessary humanitarian passage, which it does every day."
The RIA news agency quoted Rudenko as saying Russia was in touch with the United Nations on the issue.
Ukrainian Foreign Minister Dmytro Kuleba poured scorn on the suggestion that Moscow wanted to allow Ukraine to ship grain.
"You could not find a better example of a blackmail in international relations," he told the World Economic Forum in Davos. "If anyone is buying it, I think there is a problem with that person, and we shouldn't waste too much time trying to understand why that person is making that point."
Odesa is Ukraine's main deep-water port and used to handle almost all its grain exports. It has suffered a number of Russian missile attacks, and Kyiv fears that Moscow wants to capture it as it has other Ukrainian ports, potentially through an amphibious assault.
Rudenko was also quoted by Interfax as saying that any escort by Western ships of Ukrainian vessels carrying grain would "seriously exacerbate the situation in the Black Sea".
Britain said on Tuesday it had no plans to send its warships to help get food exports out of Odesa.
Euronext wheat fell to a two-week low in Paris on Wednesday after Russia said it would allow Ukrainian food exports to resume by sea under certain conditions.
Russia's defence ministry said the port of Mariupol, the Ukrainian city on the shallow-water Azov Sea which was taken by Russia after a long siege, was operating normally after Russian forces finished removing mines from there.
(Reporting by Reuters; Writing by Kevin Liffey; Editing by David Clarke, Catherine Evans and Gareth Jones)