United Nations Secretary-General Antonio Guterres is "deeply concerned" about the Ukraine Black Sea grain deal and has delayed his travel to Algiers for the Arab League Summit by a day to focus on the issue, a UN spokesperson said on Sunday.

"The Secretary-General continues to engage in intense contacts aiming at the end of the Russian suspension of its participation," UN spokesperson Stephane Dujarric said in a statement.

"The same engagement also aims at the renewal and full implementation of the initiative to facilitate exports of food and fertilizer from Ukraine, as well as removing the remaining obstacles to the exports of Russian food and fertilizer," he said.

Russia suspended participation in a UN-brokered Black Sea grain deal after what it said was a major Ukrainian drone attack on its fleet in Crimea, dealing a blow to attempts to ease the global food crisis.