Talks on a U.N and Türkiye-brokered deal that allows the safe Black Sea export of Ukrainian grain are scheduled for Wednesday, with all sides in the negotiations involved, a senior Ukrainian source said Tuesday.

"Talks are scheduled for tomorrow. All parties ... hopefully there will be results," the source, who declined to be named, told Reuters.

The deal, brokered by the United Nations and Türkiye last July, allows grain trapped by Russia's invasion to be safely exported from Ukraine's Black Sea ports.

Russia has signaled it will not allow the deal agreed on last July to continue beyond May 18 because a list of demands to facilitate its own grain and fertilizer exports has not been met.

Andrey Ledenev, a minister-counselor at the Russian Embassy in the United States, said in a post published on the embassy's Telegram messaging app that there had been no progress in removing obstacles to Russian grain and fertilizer exports.

Russia has said that parts of the deal that are meant to allow Moscow to export its own agricultural goods via the Black Sea ports were not being honored.

"There is still no progress in resolving financial and logistical problems in the shipment of Russian grain and fertilizers," Ledenev said.

"The import of agricultural equipment to Russia is difficult."

Ledenev also reiterated Moscow's long-lasting accusations that the deadlock is a direct result of the "sanction strategy" of the United States and its Western allies against Moscow, which include restrictions on payments, logistics and insurance industries.