President Donald Trump said after a two-hour call with Vladimir Putin that peace talks would begin “immediately” after his Russian counterpart refused to attend negotiations May 15 with Ukrainian President Volodymyr Zelenskyy.

Trump still wants to establish closer ties with Putin, and the White House will likely revisit the possibility of a meeting before long.

By doing so, Trump is playing into Moscow’s hands. He emboldens Putin to fight on, when Russian forces have the edge on the battlefield against a Ukraine that fears US military backing could at any mo...