United Nations (UN) Secretary-General Antonio Guterres will meet with Russian President Vladimir Putin in Moscow.
Although it will be a face-to-face meeting between Guterres and Putin, hopes for a war deal are slim, as there have been several diplomatic failures in the past.
Talks between Putin and Guterres are expected to focus on the besieged city of Mariupol, where, despite declaring victory, Russian forces have failed to take over the Azovstal steel plant.
Ukrainian forces said earlier that Russia continues to block its units at the plant. Ukraine has asked Guterres to guarantee a humanitarian corridor to evacuate civilians sheltered inside Azovstal.
The UN chief is also expected to travel to Kiev on Thursday to meet with President Volodomyr Zelensky.
While Guterres will meet with Putin, the US will also launch defense talks on Ukraine with 40 countries today.
The talks come after Moscow Foreign Minister Sergei Lavrov warned that the risk of a Third World War was "serious" and criticized Kiev's approach to disrupting peace talks.