But he condemned "brutal" deadly strikes on eastern Ukraine, saying they proved that Russia was "not thinking about how to end the war."
Trump on Friday threatened new sanctions and tariffs against Russia over its bombardment of Ukraine.
The three-year-long war is now at a critical juncture for Kyiv after Trump suspended military aid following his public falling-out with Zelenskyy last week.
Ukraine still controls some 150 square miles in the Kursk region after launching an offensive last August. Zelenskyy sees this as a possible bargaining chip in peace talks.
But Ukraine's troops in Kursk have seen their position worsen in recent weeks with Russia's army pushing back.