Russia has repeatedly painted modern Ukraine as a Nazi state, in a crass distortion of history. Putin had already seized Ukraine's Crimean peninsula eight years earlier, after a revolution that ousted Ukraine's pro-Russian president and replaced him with a more pro-Western government.

Ukraine has said its forces thwarted a surprise attack conducted by Russia through a gas pipeline in Kursk on Sunday, claiming enemy losses were “very high”.

The U.S. will use a high stakes meeting in Saudi Arabia to understand how much Ukraine is willing to give up, the secretary said.