President Donald Trump said Monday that it was "time for somebody else to negotiate on behalf of Ukraine," stepping up his criticism of Ukrainian President Volodymyr Zelensky, CNN, the Washington Examiner and CNBC reported.

Trump made the remarks as he left the White House for a campaign rally in Kansas, the Washington Examiner and CNBC reported. He was responding to a question about Zelensky saying Trump is on the "wrong side of history," the Washington Examiner reported.

"Zelensky doesn't know what he's talking about," Trump said, according to the Washington Examiner and CNBC. "Maybe it's time for Zelensky to get somebody else to negotiate," he added, the Washington Examiner reported.

Trump also said he would meet with Russian President Vladimir Putin and Chinese President Xi Jinping to discuss ending the war, and suggested Zelensky might not be present, CNBC reported. "Anything I can do to end the war, whether somebody's there or not," Trump said, according to CNBC and the Washington Examiner. The Wall Street Journal had reported that Putin floated a three-way summit with Xi next month, CNBC reported.

Trump defended easing sanctions on Moscow, including a deal on Russian diesel, despite criticism from some Republicans, the Washington Examiner reported. "Frankly, Zelensky is not helping matters much," he said, according to the Washington Examiner.

CNN reported that the relationship appears to be at its lowest point since the tense White House meeting 18 months ago. Over the weekend Kyiv launched one of its biggest drone attacks this year on Russia, hitting an oil terminal, in defiance of Trump's demand that Ukraine stop hitting Russian refineries, CNN reported.

Zelensky has said he is open to peace talks if Ukraine's security is guaranteed, CNN reported. "Ukraine never wanted this war, and we have welcomed literally EVERY attempt by our partners to bring this war to a dignified end," he said Monday, according to CNN. He also held an online meeting Monday with US lawmakers from both parties, CNN reported.

What we know: Trump said Monday someone else should negotiate for Ukraine and that he would meet Putin and Xi.
What we don't: Whether a meeting with Putin and Xi will happen, and how Kyiv will respond to Trump's call.