KYIV, Ukraine — President Donald Trump said the United States would impose sanctions on Russia if it did not accept an extended ceasefire in its war with Ukraine, writing on social media after a phone call late Thursday with Ukrainian President Volodymyr Zelenskyy.

The remark was another swivel by the administration closer to Ukraine’s positions in ceasefire talks, after two months of concessions to Russia.

During talks in Saudi Arabia in March, the Trump administration had proposed a 30-day truce to allow for peace negotiations. Ukraine accepted the idea, but Russia has pushed instead for negotiating terms for a settlement before accepting a ceasefire.

After a meeting in Vatican City with Zelenskyy on the sidelines of Pope Francis’ funeral last month, Trump threatened Russia with sanctions if it drew out of the negotiations. But his social media post after his call with Zelenskyy was his clearest statement yet that he was linking additional U.S. sanctions on Russia to its acceptance of a 30-day truce for negotiations.

— The New York Times