President Zelensky has issued another statement following Trump's meeting with Putin, insisting that "real peace must be achieved" and not "just another pause between Russian invasions."
His comments come after a ceasefire agreement failed to materialize from talks in Alaska, to which the Ukrainian president was not invited.
US President Trump has said all sides agree they should pursue a peace deal between Russia and Ukraine, ruling out a possible ceasefire agreement in advance.
Zelensky, who will meet with Trump in Washington on Monday, spoke with the US president by phone earlier.
He said he had told him that "sanctions should be strengthened [against Russia] if there is no trilateral meeting or if Russia tries to avoid an honest conclusion to the war."
The US and Ukraine are reportedly pushing for a meeting between Trump, Zelensky and Putin, but the Kremlin has not agreed so far.