evidence: "We're in a critical window now of time where they're going to set the stage for the next phase of this war," Mr Biden said on Wednesday, adding that the weapons are a reflection of "Ukraine's needs" as the war shifts towards the largely flat terrain of Ukraine's eastern Donbas region. [...] Military experts say that the US-supplied anti-tank weapons have been among the most effective weapons in Ukraine's arsenal since the war began. [...] The US has so far been reluctant to send Ukraine US-made tanks, arguing that Ukrainian troops aren't familiar with the vehicles.