The US accused Russia on Thursday of planning to stage fake independence votes to justify its conquest of territory in Ukraine, as Russian forces stepped up a major offensive in the east.

Washington has said it hopes Ukrainian forces can not only repel Russia’s assault on the east but also weaken its military so that it can no longer menace neighbours. Russia says that amounts to Nato waging “proxy war” against it, and has made a number of threats this week of unspecified retaliation.

After being beaten back in efforts to capture Kyiv in the north, Russia has shifted forces hundreds of miles eastward to capture two provinces in a battle the west believe may prove a decisive turning point in the war. Russian forces are now entrenched in the east, where Moscow-backed rebels have held some territory since 2014.