US President Donald Trump has said he thinks "it's time for Ukraine to get a new president" as he responded to Volodymyr Zelensky's criticism of the US diesel deal with Russia. The Ukrainian president warned a new deal to release millions of tonnes of Russian diesel into the US would provide Moscow with money to continue its war against his nation, calling it a gift to Russian President Vladimir Putin. Trump told reporters outside the White House on Saturday that Zelensky "wants to make problems for the world" by continuing to authorise attacks on Russian refineries.