The Kremlin said on Friday the Ukraine war was "existential" for Russia, after it launched a wave of retaliatory drone and missile strikes that killed three rescue workers in Kyiv. Peskov's comments came shortly after the Russian defence ministry said its forces had launched the "massive" missile and drone strike in "response" to recent attacks by Kyiv on its territory.

But halting progress, ever-more deadly drone attacks and unmoving negotiating positions seem to have taken their toll. On Thursday, Trump used a striking analogy to concede the warfare was nowhere near over, and that he did not, at that moment, feel it was best to intervene.

The German chancellor had come to Washington hoping to persuade President Trump to play a more active role in defending Ukraine.