Kyiv has lost five of the 31 Abrams tanks given to it by the US to Russian attacks since October last year. Ukraine had engaged in a months-long campaign arguing that the tanks, which cost about $10m apiece, were vital to its ability to breach Russian lines.

Ukraine for the first time has begun using long-range ballistic missiles provided secretly by the United States, bombing a Russian military airfield in Crimea last week and Russian forces in another occupied area overnight.