The Russian Foreign Ministry issued a stark warning to the US on Thursday, stressing that Russia “does not accept threats” following US President Donald Trump‘s statements about an ultimatum to the Kremlin to end the war in Ukraine.

Trump, adopting a tougher stance toward Moscow, announced on Monday that he was giving a 50-day deadline for Russia to reach a ceasefire in Ukraine, warning that new sanctions would otherwise follow. At the same time, it pledged to send additional missiles and equipment to Kiev, strengthening Ukraine’s war machine.

Responding to the US president’s statements, Russian Foreign Ministry spokeswoman Maria Zakharova denounced Trump’s decision to send new missiles as a “signal for the continuation of the massacre” and a rejection of any peace initiative.

At the same time, Zakharova said that negotiations “between Russia and Ukraine are ‘stuck’ on the part of Kiev, which is either avoiding or has not decided on the date of a new round.”