"It's very difficult, sometimes confrontational," Zelensky said in an address to his nation this morning. "But step by step we are moving forward."
Western nations are planning further sanctions against Russia.
Over 300 members of Russia's lower house of parliament are expected to be sanctioned by the US on Thursday.
"No final decisions have been made about who we will sanction and how many we will sanction," the White House said. "We will have additional sanctions measures to announce that will be rolled out in conjunction with our allies on Thursday when the President has the opportunity to speak with them."
US President Joe Biden visits Brussels this week and is expected to announce a new round of sanctions. His visit will also include a trip to Poland and discussions around Europe's energy security.
The UN human rights office claims 953 civilians have died since the Russian invasion of Ukraine, with 1,557 injured. The Kremlin denies that it is targeting civilian areas.
Ukraine claims that hundreds of women and children are buried under rubble in the city of Mariupol after Russian bombs targeted public buildings including schools and a theatre. Officials in Kyiv have accused Russia of "kidnapping" 2,389 children from the Luhansk and Donetsk regions, but Russia claims it is simply taking in refugees.
