Russian President Vladimir Putin told President Donald Trump in a phone call Wednesday that he was obligated to respond to Ukraine’s weekend drone attack, Trump said, setting up a potential escalation in the conflict just as the US president hopes to broker an end to the war.

WASHINGTON (AP) — U.S. President Donald Trump said that Russian President Vladimir Putin told him “very strongly” in a phone call Wednesday that he will respond to Ukraine’s weekend drone attack on Russian airfields as the deadlock over the war drags on and Ukrainian President Volodymyr Zelenskyy dismisses Russia’s ceasefire proposal.