Talks between a Russian delegation and senior UN officials to address Moscow's grievances about the Black Sea grains export initiative began in Geneva on Friday, a UN spokesperson said.
The accord has helped stave off a global food crisis by allowing the export of food and fertilisers from several of Ukraine's Black Sea ports.
Moscow has indicated that it is prepared to quit the deal, which could expire on 19 November, if progress is not made on its concerns. Russia suspended its participation in late October but rejoined after four days.
It said it was responding to a drone attack on Moscow's fleet in Crimea that it blamed on Ukraine. Kyiv has not claimed responsibility and denies using the grain programme's security corridor for military purposes.
UN aid chief Martin Griffiths, who heads talks on Ukrainian exports, and senior UN trade official Rebeca Grynspan, are meeting with Russia's deputy foreign minister Sergei Vershinin at the UN office in Geneva, Alessandra Vellucci, spokesperson for the United Nations in Geneva, said.
"This discussion, it is hoped, should advance progress made in facilitating the unimpeded export of food and fertilisers originating from the Russian Federation to the global markets," she told a news briefing.
Vellucci made no mention of whether an extension of the pact was on the agenda.