UN Secretary-General Antonio Guterres described the first round on July 13 as a "substantive step" to an agreement that could avert a global food crisis.
Turkish President Recep Tayyip Erdogan said after a summit with Russian President Vladimir Putin and Iranian President Ebrahim Raisi in Tehran on Wednesday that a formal agreement would hopefully be signed at the second meeting.
Putin has called for a "package solution" that would also remove hurdles that Western sanctions had brought up against Russian grain exports to the detriment of the global food security.
Ukraine and Russia account for a combined 30% of the world's wheat exports, 20% of maize, and 76% of sunflower.
The European Union published clarifications to the sanctions on Thursday containing a waiver of transaction limits related to Russian agricultural products. It said it never meant to target trade in wheat and fertilizers between Russia and third countries.
The EU, the United States, and the UN’s World Food Programme have expressed cautious optimism that the flow of grain across the Black Sea would resume following the talks on Friday.
Russia has repeatedly argued that maritime mines planted by Ukrainian troops at the entrance to the Black Sea ports had prevented merchant ships from safely getting grain out of Ukraine.