Ukraine, by its actions, gave Russia grounds for a massive strike, US President Donald Trump told reporters. "Ukraine gave [to Russian President Vladimir] Putin has a reason to go and bomb them to hell," he said.

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.

President Trump compared Russia and Ukraine with "children fighting in the park" on Thursday and suggested it might be better to let them keep on fighting for a while.