A crucial deal aimed at averting a global food crisis following Russia's invasion of Ukraine has been extended for two months.

Turkish President Recep Tayyip Erdogan said Wednesday an agreement has been reached with Russia and Ukraine to extend the Black Sea grain deal.

Ukraine is one of the world's leading grain exporters but after the war began, Russia blockaded Ukrainian ports, sparking fears of a global famine.

Since last summer, an agreement between the two sides has enabled the safe passage of ships from Ukraine. It is the first and only major pact to be made between the warring sides since the outbreak of the war.

The deal has now been resuscitated for a third time after a question mark hung over its survival. Here's what you need to know.

What is the Black Sea grain deal and why is it important?

The Black Sea grain deal was first reached in July 2022.

Russia had been blockading vital grain exports from key Ukrainian Black Sea ports, including Odesa, Chornomorsk, and Pivdennyi. US intelligence also indicated that Russian forces were deploying mines in the Black Sea.

The blockages meant that millions of tons of Ukrainian grain were not being exported to the many countries that rely on it.

The impact of the war on global food markets was immediate and extremely painful, especially because Ukraine is a major supplier of grain to the World Food Programme (WFP). According to the European Commission, Ukraine accounts for 10% of the world wheat market, 15% of the corn market, and 13% of the barley market. It is also a key global player in the market of sunflower oil.

The Food and Agriculture Organization (FAO), an UN body, warned at the time that as many as 47 million people could be pushed into "acute food insecurity" because of the war. Western officials accused Russia of using food as a weapon.

The deal -- brokered by the United Nations and Turkey with Russia and Ukraine -- created procedures to ensure the safe export of grain from Ukrainian ports.

As part of the deal, grain ships were able to navigate through a safe corridor in the Black Sea under the direction of Ukrainian pilots, and then pass through the Bosphorus Strait -- an important shipping corridor in north-west Turkey -- in order to reach global markets.

The agreement has proven vital for stabilizing global food prices and bringing relief to the developing countries who rely on Ukrainian exports.

Since being struck the deal has enabled an estimated 900 ships to safely leave Black Sea ports, delivering 24 million tons of grain to countries as far afield as Africa and the Middle East.

Who are the main players?

The Black Sea grain deal was an agreement made between Russia and Ukraine -- however, it was not a direct agreement. During its signing in Istanbul, representatives from Russia and Ukraine did not sit together during the ceremony, the Washington Post reported at the time.

NATO-member Turkey, who has positioned itself as an intermediary between Kyiv and Moscow since the beginning of the conflict, brokered the rare deal with the United Nations.

As part of its role in the pact, Turkey carries out inspections on all the merchant vessels that pass through the Black Sea in specially established safe corridors.

Another key creation of the deal is the Joint Coordination Center (JCC), which was set up in Istanbul under the auspices of the UN.

The JCC comprises 20 officials -- five representatives each from Russia, Ukraine, the UN and Turkey -- and is tasked with monitoring the movement of the vessels and ensuring that all sides are complying with the Initiative.

Why was its renewal for a third time in question?

The deal's survival rests in Russia's hands. Prior to its third renewal, the Kremlin had remained elusive as to whether it would remain in the pact.

The deal was initially brokered for a period of 120 days and was set to expire in November last year.

Russia suspended its participation for a few days in late October and early November last year, citing drone attacks on the city of Sevastopol in occupied Crimea. Moscow later announced that it would reverse course and rejoin the agreement for a further 120 days, following mediation.

The deal was renewed in March for another 60 days and is due to expire again on Thursday, May 18.

Prior to Wednesday's announcement, it remained unclear whether the agreement would be renewed for a third time after two days of urgent talks in Istanbul earlier this month failed to reach a decisive outcome.

Russia had once again threatened to quit the deal and cited a list of demands, largely over exports of its own food stuffs and fertilizers.

Moscow repeatedly complained that a separate agreement with the UN to facilitate shipments of Russian fertilizers and grain, which was brokered as part of the package last July, had not yielded results.

The Kremlin has also warned it would scrap the deal if the Group of Seven (G7) nations imposed further bans on exports to Russia as part of sanctions over its invasion of Ukraine. Bloomberg reported last month that G7 officials are considering whether to impose an outright ban on almost all exports to Russia, placing further economic pressure on the country.

Russian Deputy Foreign Minister Sergei Vershinin warned after the talks in Istanbul that if there was no consensus by May 18, the deal would "cease to exist."

On Wednesday, on the brink of its expiry, Erdogan confirmed the deal would be extended for a further two months. This was followed by confirmation from Ukrainian and Russian officials.

Oleksandr Kubrakov, the Ukrainian minister of communities, territories and infrastructure development, said on Facebook: "The grain deal has been unblocked and will continue to be in effect until July 18. The world will continue to receive Ukrainian products thanks to the efforts of our partners in the agreement - Turkey and the UN.

"We are grateful to our partners for their unwavering and focused position that the agreement should continue to work and on the terms signed by all parties."

However, Russian Foreign Ministry spokeswoman Maria Zakharova warned: "Distortions in the implementation of the grain deal should be corrected as quickly as possible."

Does everyone gain from the grain deal?

Not quite. Following Russia's blockade, the European Union lifted all duties on grain from Ukraine via land, to facilitate exports.

This, though, caused a glut of cheap Ukrainian grain to flow into central and eastern Europe, hitting the sales of local producers.

Demonstrators last month blocked traffic and border checkpoints with tractors along the border between Romania and Bulgaria, in an effort to prevent Ukrainian trucks from entering their country.

These visible signs of discontent were significant in a region of the world that has been consistently supportive of Ukraine in the face of Russian aggression. As BulgarianAgriculture Minister Yavor Gechev said: "Bulgaria is in solidarity with Ukraine, but a local glut is being created on the agricultural market, because instead of export corridors our countries are becoming warehouses."

To quell the unrest, the EU subsequently adopted a temporary measure that bans wheat, maize, rapeseed and sunflower seed originating in Ukraine from being exported to Bulgaria, Hungary, Poland, Romania and Slovakia.

This move, however, was criticized by Ukrainian President Volodymyr Zelensky, who slammed the "protectionist measures" as "completely unacceptable."