As the United Nations and Turkish officials work to reach a written agreement with Russia and Ukraine to resume Ukraine’s Black Sea grain exports, U.N. Secretary-General Antonio Guterres will visit Istanbul later on Thursday, according to a U.N. spokesperson.

According to deputy U.N. spokesman Farhan Haq, who spoke to reporters in New York, “the situation remains rather fluid, so I can’t really say when something will be signed.” “We’re still not there,”

Turkish Foreign Minister Mevlut Cavusoglu said on Thursday that he was hopeful about reaching a deal and that talks were going well. Ankara said a general agreement was reached on a U.N.-led plan during talks in Istanbul last week and that it wants to put this into writing this week.

Before last week’s talks, diplomats said details of the plan included Ukrainian vessels guiding grain ships in and out through mined port waters; Russia agreeing to a truce while shipments move; and Turkey – supported by the United Nations – inspecting ships to allay Russian fears of weapons smuggling.

The United Nations and Turkey have been working for two months to broker what U.N. Secretary-General Antonio Guterres called a “package” deal – to resume Ukraine’s Black Sea grain exports and facilitate Russian grain and fertilizer shipments.

Russia and Ukraine are both major global wheat suppliers, but Moscow’s Feb. 24 invasion of its neighbor has sent food prices soaring and stoked an international food crisis. The war has stalled Kyiv’s exports, leaving dozens of ships stranded and some 20 million tonnes of grain stuck in silos at Odesa port.

Moscow has denied responsibility for worsening the food crisis, blaming instead a chilling effect from Western sanctions for slowing its own food and fertilizer exports and Ukraine for mining its Black Sea ports.

A day after the Istanbul talks last week, the United States sought to facilitate Russian food and fertilizer exports by reassuring banks, shipping and insurance companies that such transactions would not breach Washington’s sanctions on Moscow over its invasion of Ukraine.