The Kremlin said Trump had raised “the issue of an immediate ceasefire” in the call, their sixth known call since Trump returned to the White House in January, but the Russian leader said he “will not back down.”

“Vladimir Putin stated that Russia continues to seek a political resolution to the conflict through negotiations,” Kremlin’s foreign policy aide Yuri Ushakov said in a briefing Thursday.

But the Kremlin has so far not offered concessions on its central demands that Ukraine should cede territory and give up on joining NATO.

While Kyiv or the White House did not say what the call would involve, Zelenskyy is widely expected to renew his calls for more military aid and U.S. sanctions against Russia. Ukraine is still reeling from Trump’s decision this week to halt some U.S. military equipment deliveries, which include the vital air defense systems.

“Without truly large-scale pressure, Russia will not change its dumb, destructive behavior,” Zelenskyy said, stressing that it “primarily” depends on the U.S. to “change the situation for the better.”

Michael Bociurkiw, a senior fellow at the Atlantic Council think tank, said Trump’s inaction, and his outright blaming of Ukraine at times, is likely seen by Putin as an invitation to press forward on the battlefield.

“Putin sees this as almost an invitation to bomb, bomb the heck out of Ukrainian cities and to grab more territory,” said Bociurkiw said in a telephone interview from the southwestern Ukrainian city of Odessa.