MOSCOW The Kremlin said on Wednesday that Russia's stance on the Black Sea grain deal - that its own interests must be taken into account in talks aimed at extending it beyond May 18 - was understood by all relevant parties.

Four-way talks on the deal, between Russia, Ukraine, Turkey and the United Nations - are due to take place in Istanbul this week.

"Work is underway. Our position is well known... and consistent," Kremlin spokesman Dmitry Peskov told reporters.

"So, let's wait for the outcome of the negotiations."

The United Nations and Turkey brokered the Black Sea export agreement in July to help tackle a global food crisis that has been worsened by Moscow's war in Ukraine.

To help convince Russia to allow Ukraine to resume Black Sea grain exports, a three-year pact was also struck in July in which the U.N. agreed to help Moscow facilitate its own agricultural exports, something it complains hasn't happened at scale.

Both Ukraine and Russia say the Black Sea grain deal, which allowed Ukrainian exports via the Black Sea, is in danger of collapsing.

Russia and Ukraine are two of the world's key agricultural producers, and major players in the wheat, barley, maize, rapeseed, rapeseed oil, sunflower seed and sunflower oil markets. Russia is also dominant in the fertiliser market.

While Russian agricultural exports are not subject to Western sanctions imposed following the February 2022 invasion of Ukraine, Moscow says restrictions on payments, logistics and insurance are a significant barrier to shipments.

(Reporting by Reuters; editing by Guy Faulconbridge/Andrew Osborn)