MOSCOW: Russian President Vladimir Putin and Turkish counterpart Recep Tayyip Erdogan will meet Tuesday in Tehran to discuss Ukraine grain export mechanisms, a Kremlin source said Monday.

The two leaders will meet in the Iranian capital with the conflict in Ukraine massively hampering shipments from one of the world’s biggest exporters of wheat and other grain, sparking fears of global food shortages.

“Firstly, we are ready to continue the work in this direction, secondly this issue is going to be discussed by the presidents,” Russian news agencies quoted presidential advisor Yuri Ushakov as saying.

The Russian defence ministry had indicated Friday that a “final document” on the subject mediated by the UN would be soon ready to release some 20 million tons of currently blocked grain exports as well as those of Russian grain and fertiliser currently held back under Western sanctions.

According to Ushakov, a coordination centre is to be opened in Istanbul allowing routing of those exports via the Black Sea.

Turkish Defence Minister Hulusi Akar confirmed for his part Monday that “an agreement in principle … has been found” between Ukraine and Russia to establish a secure sea corridor allowing grain transport.

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Turkey – a NATO member on speaking terms with both Russia and Ukraine – has spearheaded efforts to resume the grain deliveries.

An official Turkish source requesting anonymity said another meeting could take place “Wednesday or Thursday”, following the Tehran talks.

The news that Putin and Erdogan are to meet came on a day which saw EU foreign policy chief Josep Borrell warn Russia’s blockade of Ukrainian ports threatens supplies to countless thousands vulnerable to starvation.

Borrell dubbed the issue “one of life and death for many human beings.”

Russian and Ukrainian negotiators were already scheduled to meet UN and Turkish diplomats in Istanbul on Wednesday to discuss a possible agreement to end the months-long blockade of Ukraine’s ports following the February invasion.

Russia has captured some Black Sea ports and bombarded others, including the key grain exporting outlet in the city of Odessa. Ukraine has meanwhile mined the approaches to some of its ports to protect them from Russian assault.

Ukraine’s farms are a major source of grain for the world market, in particular in the Middle East and Africa, where food supplies are critically tight.