Christiane Amanpour speaks to Fiona Hill, former National Security Council Senior Director for Russian Affairs.

Trump previously said his personal relationship with Putin would usher in peace for Ukraine. Now, he says Putin's gone "absolutely CRAZY!"

A Russian official said "Trump is not being sufficiently informed about what is really happening in the context of the Ukrainian-Russian confrontation."

However, Trump’s rhetoric surrounding Russia, traditionally sympathetic to Putin’s aims, has shifted in recent weeks as his attempts to end the war continue to be thwarted.At the weekend, Trump warned that if Putin threatened to conquer all of Ukraine he would bring about the “downfall” of Russia.

Hundreds of Ukrainian drones crossed into Russia overnight into Wednesday morning, dozens of which targeted Moscow.

Ukraine says Russia launched its biggest drone strike to date after Trump called Putin crazy for stepping up his offensive and "needlessly killing a lot of people."

By Steve Holland, Tom Balmforth and Yuliia Dysa WASHINGTON/KYIV (Reuters) -U.S. President Donald Trump on Tuesday said Vladimir Putin was "playing with fire" by refusing to engage in ceasefire talks with Kyiv as Russian forces made gains in Ukraine's northeast.

But in recent weeks, the relationship has begun to show signs of strain.

The White House faces the question of whether its appeasement of Russia has failed to achieve the ceasefire it promised and instead emboldened the Kremlin on the battlefield.