Zelenskyy said the letter was meant to thank the first lady for raising awareness about children abducted from Ukraine.

Mr. Trump said any guarantees would involve U.S. "coordination."

President Donald Trump said he’s begun arrangements for a face-to-face meeting between Vladimir Putin and Volodymyr Zelenskyy to discuss a pathway to end Russia’s invasion of Ukraine.

Trump helped bring Thailand to the table for talks after long-simmering tensions with Cambodia spilled over in July into a five-day military conflict, the deadliest fighting there in over a decade.