U.S. Permanent Representative to the UN Linda Thomas-Greenfield has arrived in Ukraine on a visit, Director of Communications and Press Secretary of the U.S. Mission to the UN Nate Evans has said.

"The U.S. Ambassador to the UN is in Kyiv for a day of meetings to reiterate US's unwavering support for Ukraine as it defends its freedom and sovereignty amidst Russia's brutal and unprovoked invasion," Evans said onTwitter on Tuesday.

While in Kyiv, Thomas-Greenfield will meet with Ukrainian government leaders to discuss the unwavering U.S. commitment to Ukraine's sovereignty and independence, according to the U.S. Embassy in Ukraine. She will oversee efforts to document and preserve evidence of atrocities committed by Russian forces and hear first-hand accounts from survivors.

Ambassador Thomas-Greenfield will also discuss the global food security crisis exacerbated by Russia's invasion and stress the urgent need to extend the Black Sea Grain Initiative into next year. She will also meet with humanitarian organizations working to meet the winterization needs of vulnerable populations affected by Russian attacks on energy and other civilian infrastructure.