One expert warned that if NATO "falls for this, we'll get ourselves in real trouble" amid Vladimir Putin's posturing.

Amid ongoing high-level meetings between NATO leaders and Ukrainian officials at the United Nations over plans to allow Ukraine to strike Russian cities with NATO weapons, Russian President Vladimir Putin outlined Wednesday a proposed update to Russia’s nuclear policy document that would expand the conditions under which Russia would use nuclear weapons.

The Kremlin said on Thursday that changes to Russia's nuclear weapons doctrine outlined by President Vladimir Putin should be considered a signal to Western countries that there will be consequences if they participate in attacks on Russia.