ANKARA, Turkey — Turkish officials say a deal on a U.N. plan to unblock the exports of Ukrainian grain amid the war and to allow Russia to export grain and fertilizers will be signed Friday in Istanbul.

Turkish President Recep Tayyip Erdogan’s office said that he, U.N. Secretary General Antonio Guterres and officials from Russia and Ukraine will oversee the signing ceremony. It did not provide further details.

“The grain export agreement, critically important for global food security, will be signed in Istanbul tomorrow under the auspices of President Erdogan and U.N. Secretary General Mr. Guterres together with Ukrainian and Russian delegations,” Erdogan spokesman Ibrahim Kalin said in a tweet.