UN Secretary-General Antonio Guterres sent Russian President Vladimir Putin a letter on Tuesday proposing a way forward to further facilitate Russian food and fertiliser exports and ensure the continued Black Sea shipments of Ukrainian grain, Reuters reported.

"The objective is to remove hurdles affecting financial transactions through the Russian Agricultural Bank, a major concern expressed by the Russian Federation, and simultaneously allow for the continued flow of Ukrainian grain through the Black Sea," UN spokesman Stephane Dujarric told reporters on Wednesday.

A deal allowing the safe Black Sea exports of grain and fertilisers from Ukraine is due to expire on Monday.