A Russian presidential aide has cast doubt on the US plan for a ceasefire in Ukraine, as American special envoy Steve Witkoff arrived in Moscow.

Russian leaders comments signal that there will be difficult negotiations ahead that could frustrate President Donald Trump’s hope for a swift peace deal.

Russian President Putin said he supports the idea of President Trump’s ceasefire plan, but there are issues he needs to discuss with the U.S. before he would agree to it. President Trump called Putin’s comments “very promising” but incomplete.

Zelensky's comments come after Putin agreed fighting must end but any plan must remove the "underlying causes of this crisis".

Ukraine’s consent to a 30-day ceasefire proposal has handed the Kremlin a difficult challenge at a time when its military has an upper hand in the war.