Paragraph 4 of the Budapest Memorandum states that 'the signatories (US, UK, Russia) reaffirm their commitment to seek immediate UN Security Council action to provide assistance to Ukraine, as a non-nuclear-weapon State Party to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), if Ukraine should become a victim of an act of aggression or an object of a threat of aggression in which nuclear weapons are used'…