US President Donald Trump said he believed "it's time for a new president in Ukraine", responding to Volodymyr Zelensky's criticism of the US-Russia diesel deal.
Ukraine's president warned that a new deal to allow millions of tons of Russian diesel into the United States would provide money for Moscow to continue its war on Ukraine. He called it a gift to Russian President Vladimir Putin.
Trump told reporters outside the White House on Saturday that Zelensky "wanted to cause trouble for the world" by continuing to approve attacks on Russian refineries.
"He better stop," Trump said, before suggesting Ukraine should "get a new leader who can make a deal."
Ukraine has been under martial law since Russia invaded the country in 2022, meaning elections have been suspended.
The war waged by the United States and Israel against Iran has severely restricted global fuel supplies, including diesel. The war resulted in the virtual closure of the Strait of Hormuz, through which about a fifth of the world's petroleum products are normally transported.
Russia, as a major producer, and Ukraine have recently stepped up attacks on each other's energy infrastructure and transportation facilities, further exacerbating tensions in the energy market.
"We said, 'You can do whatever you want to do to Russia, but don't hit the refineries,' because that will create a global problem," Trump continued.
"He could have made a lot of deals, but for whatever reason he never did."
Putin's envoy Kirill Dmitriev called Trump's intervention "landmark and historic" and said Ukraine "needs leadership that is truly focused on peace."
The US president confirmed on Friday that he had reached an agreement with Moscow to suspend sanctions on Russian diesel exports until April 7.
Zelensky responded that this would allow Moscow to raise new funds and purchase new military equipment to continue the war.
He also accused Moscow of interpreting the agreement "to mean that they can continue to fight, to mean that they can continue to drop bombs on cities" after a new round of deadly attacks in Zaporizhzhia.
Ukraine's president held a phone call with several allies on Saturday to discuss the latest developments and called for "real decisions to be taken to protect the lives of Ukrainian people" and to safeguard European security.
A Downing Street spokesman said British Prime Minister Andy Burnham had spoken to Zelensky and expressed his "full support" for him.
The spokesman said the two men agreed that Russia should agree to "immediately cease fighting against energy facilities" and stop attacks on Black Sea shipping because "this would immediately allow more energy and food supplies to enter global markets."
News of the US-Russia diesel deal was also criticized by EU foreign affairs chief Kaja Kallas. Echoing Zelensky, she said the suspension of sanctions "provides Moscow with more revenue to wage war," adding: "Now is not the time to reduce pressure on Russia, and Europe will not do that."
She said European foreign ministers planned to approve on Monday the largest round of sanctions since Russia launched its full-scale invasion.
The deal with Russia is Trump's latest move to lower U.S. fuel prices ahead of the midterm elections, after spending months grappling with the political fallout from the war with Iran.
The conflict, which began in February, has sent gasoline and especially diesel prices soaring, eroding his support among the American public. Americans have been hit by rising gas prices at the pump and their knock-on effects, which have led to widespread price increases.
Diesel prices currently average $6.28 per gallon, according to AAA, up from last month's average of $5.94 per gallon and up from last year's $3.68 per gallon.
Under the agreement, Russia will initially supply 300,000 tons of diesel to "the U.S. and global markets", followed by a further 500,000 tons in November.
Trump wrote on Truth Social that another 1 million tons would be supplied later, and another 3 million tons "in a short period of time." But he pointed out that whether the diesel can be delivered will "depend on the status of their diesel refinery."
The International Energy Agency estimates that Russian diesel production has fallen by 30%.
Trump had previously called for Ukraine to hold new elections in December last year, saying that Ukrainian voters should have the opportunity to choose to replace Zelensky.
