This study adopts a critical discourse analysis approach to examine the strategies employed by US President Joe Biden in his speeches to de-legitimize the Russian war in Ukraine that started in 2022. The study applies van Leeuwen's (2007) (de) legitimation strategies model. Two speeches, extracted from the White House official website and delivered by President Biden on two different occasions during the first few months of the war being waged, are analyzed. The results reveal US President Biden's tendency to rely mainly on three de-legitimation categories. The most frequently employed strategy is moral evaluation through evaluative modifiers and abstraction. The second most frequent strategy is authorization mainly through authority of conformity, in addition to impersonal and personal authority. Finally, both instrumental and theoretical rationalization are employed to delegitimate the Russian war in Ukraine and legitimize the US assistance provided to it.