United Nations Secretary-General Antonio Guterres says there is "progress" in talks to allow the export of grain stored in Ukrainian ports and ensure Russian food and fertilizer have unrestricted access to global markets.

"I think that there is progress, but we are not yet" there, Guterres said Wednesday, adding "these are very complex things," because "everything is interlinked."

Russia's war on Ukraine has closed the country's Black Sea ports, halting food exports to many developing countries.

Guterres reiterated the world should have access to the Russian production of fertilizers and foods "that is also essential for global markets in the present situation."

Guterres spoke in Stockholm where he met with Swedish Prime Minister Magdalena Andersson ahead of a climate and environment conference Thursday and Friday.

Russian Foreign Minister Sergei Lavrov on Wednesday said international sanctions are affecting Russia's ability to export its own grain amid fears of a global food shortage.

Speaking during a visit to Saudi Arabia, Lavrov said Russian grain exports might not be directly under sanctions, but the ships carrying the grain face extra hurdles.

"Although the West very loudly reminds that grain was not subject to sanctions, for some reason they shyly keep silent that ships that carry Russian grain did fall under the sanctions," he said.

"They are not accepted in foreign ports, in European ports, and they are not insured. And, in principle, all the logistical and financial chains related to the supply of grain to world markets, they were under the sanctions of our Western colleagues."

Russia has also been accused of preventing Ukraine from exporting its grain harvest and of looting Ukrainian grain supplies for Russian use.