President Vladimir Putin warned Russia would be “at war” with the United States and its allies if they allow Ukraine to strike deeper inside Russia with long-range Western weapons.

Dmitry Medvedev, a long-time ally of Russian President Vladimir Putin, has laid out the country's new deterrence policy against Western "aggression," and warned that provocations by Ukraine and its allies could result in nuclear war.

A close ally of President Vladimir Putin warned Western governments on Thursday that a nuclear war would ensue if they gave the green light for Ukraine to use long-range Western weapons to strike targets deep inside Russia.