U.N. Secretary-General Antonio Guterres will travel to Istanbul on Thursday, a U.N. spokesperson said as United Nations and Turkish officials seek to get a deal with Russia and Ukraine in writing to resume Ukraine's Black Sea grain exports, News.az reports citing Anadolu.

"The situation remains a little bit fluid, so I can't really say when something will be signed," deputy U.N. spokesman Farhan Haq told reporters in New York. "We're not quite there yet."

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.