Details of the emerging deal, brokered by the United Nations and Turkey with Russia and Ukraine have not yet been divulged.
The agreement will be signed on Friday morning local time in Istanbul, Turkey's communications directorate said.
However, more talks are expected before the agreement is signed, a top Ukrainian official has cautioned.
"Following negotiations, a document can be signed, that will contain the obligations of the parties regarding the safe operation of the export routes in the Black Sea," Oleg Nikolenko, the spokesperson for Ukraine's Ministry of Foreign Affairs, said Thursday evening.
Nikolenko stressed that the Ukrainian delegation "will support only those decisions that will guarantee the security of the southern regions of Ukraine, the strong positions of the Ukrainian Armed Forces in the Black Sea, and the safe export of Ukrainian agricultural products to the world markets."
United Nations Secretary-General Antonio Guterres traveled to Istanbul on Thursday to work on easing access to Ukrainian and Russian food products. The parties sought to reach an "agreement that would allow for Ukrainian and Russian food and fertilizer to reach global markets," according to spokesman Farhan Haq.
Ukraine and Russia are both significant suppliers of food to the world. In normal times, Ukraine -- known as one of the globe's breadbaskets -- would export around three-quarters of the grain it produces. According to data from the European Commission, about 90% of these exports were shipped by sea, from Ukraine's Black Sea ports.
Russia is currently blocking maritime access to those ports, meaning that millions of tons of Ukrainian grain cannot be exported to the many countries that rely on it.
Between disrupting Ukrainian agricultural production and blocking the export of products that remain, Russia's war in Ukraine could push 49 million people into famine or famine-like conditions, the United Nations warned last month.
Western officials have accused Russia of deliberately strangling the global supply chain. European Commission Chief Ursula von der Leyen said that food was part of the Kremlin's "arsenal of terror," and the US accused it of having "weaponized" food.
The US on Thursday hailed the "agreement in principle," but State Department spokesman Ned Price cautioned that the deal is still "very early going" and said Washington would focus on "holding Russia accountable for implementing this agreement."
European officials familiar with the discussions also expressed optimism about the agreement, but cited concerns about its implementation.
The officials said that Russia is unlikely to follow-through on the agreement without any issues.