Mr. Putin claimed that Kyiv’s response would shed light on Ukraine’s “desire, and, indeed, its ability” to take part in negotiations to end the war. President Volodymyr Zelensky of Ukraine referred to the announcement as Mr. Putin’s “next attempt to play with people’s lives,” without specifying whether Ukraine would also observe a truce.

Trump spoke shortly after Marco Rubio warned that the U.S. may “move on” from trying to secure a Russia-Ukraine peace deal if there is no progress in the coming days.