On Monday, U.N. aid chief Martin Griffiths said that talks to extend the Black Sea grain deal would continue over the coming days as Russia's deadline nears.

The deal is set to expire on May 18.

Türkiye, Russia, Ukraine and the U.N. held a two-day high-level meeting in Istanbul last week to discuss extending the grain deal, but no agreement was reached.

"Continuation of the Black Sea Initiative is critically important," Griffiths, the under-secretary-general for humanitarian affairs and emergency relief coordinator, told the U.N. Security Council.

"In recent weeks, we have engaged in intensive discussions with the parties to the Black Sea Initiative to secure agreement on its extension and the improvements needed for it to operate effectively and predictably. This will continue over the coming days."

Meanwhile, Ukraine on Monday acknowledged the possibility that the agreement may end on May 18 and said no further negotiations are planned for this week.

Olha Trofimtseva, a Foreign Ministry ambassador, told a briefing that Ukraine was receiving conflicting signals about the deal's future.

In order to agree to another extension of the grain deal, signed in Istanbul last July among the four parties, Russia is seeking the removal of obstacles to its fertilizer exports.

There are no Western sanctions on Russian exports of food and fertilizer, but Russia says banking restrictions impact its exports.

Türkiye, the U.N., Russia and Ukraine signed an agreement last July in Istanbul to resume grain exports from the Ukrainian ports, paused after the Russia-Ukraine war began in February, to help tackle a global food crisis.

According to the U.N., over 30 million metric tons of grain and foodstuffs have been exported from Ukraine since last August.