A senior UN official had “constructive discussions” in Moscow with Russian First Deputy Prime Minister Andrei Belousov on facilitating Russian grain and fertilizer exports to global markets, UN spokesman Stephane Dujarric said on Tuesday.

The UN official, Rebecca Grynspan, is now in Washington for talks on the same issue “with the key aim of addressing growing global food insecurity,” Dujarric said.

US Ambassador to the United Nations Linda Thomas-Greenfield said the United States is prepared to give “comfort letters” to shipping and insurance companies to help facilitate exports of Russian grain and fertilizer.

She noted that Russian grain and fertilizer were not directly sanctioned by the United States but that “companies are a little nervous and we’re prepared to give them comfort letters if that will help to encourage them.”

UN Secretary-General Antonio Guterres, who visited Moscow and Kyiv last month, is trying to broker what he calls a “package deal” to resume both Ukrainian food exports and Russian food and fertilizer exports.

Russia’s war in Ukraine has fueled a global food crisis with prices for grains, cooking oils, fuel and fertilizer soaring. Russia and Ukraine account for nearly a third of global wheat supplies, while Russia is also a key fertilizer exporter and Ukraine is a major exporter of corn and sunflower oil.

Since Russia invaded on Feb. 24, Ukrainian grain shipments from its Black Sea ports have stalled and more than 20 million tonnes of grain are stuck in silos, while Moscow says the chilling effect of Western sanctions imposed on Russia over the war has disrupted its fertilizer and grain exports.

Russian President Vladimir Putin said on Monday that Russia was ready to facilitate the unhindered export of grain from Ukrainian ports in coordination with Turkey, according to a Kremlin readout of talks with President Tayyip Erdogan.

“The Secretary-General is extremely grateful for the support that Turkey is giving in addressing the situation in the Black Sea and supporting the Secretary-General’s own efforts,” Dujarric said.