Trump has horrified European allies with his attacks on Volodymyr Zelenskyy and what critics say is a soft take on Vladimir Putin.

Trump called the Ukrainian president a 'dictator,' as European leaders try to assert more control over negotiations.

Russian President Vladimir Putin said on Monday that Russia was not opposed to Europe's involvement in Russia-U.S. peace talks aimed at settling the conflict in Ukraine, but noted that Brussels had long rejected any dialogue with Moscow.