Russian President Vladimir Putin's spokesman conceded on Tuesday that Russia has yet to achieve any of its military goals in Ukraine and refused to deny that Moscow could resort to the use of nuclear weapons.

Speaking to CNN's Christiane Amanpour, the spokesman, Dmitry Peskov, repeatedly refused to rule out that Russia would consider using nuclear weapons against what Moscow saw as an "existential threat."

Asked under what conditions Putin would use Russia's nuclear capability, Peskov replied, "if it is an existential threat for our country, then it can be."

Putin has previously hinted at using nuclear weapons against nations that he saw as a threat to Russia. In February, the Russian President said in a televised statement, "No matter who tries to stand in our way or all the more so create threats for our country and our people, they must know that Russia will respond immediately, and the consequences will be such as you have never seen in your entire history."

He then said in a televised meeting with Russian defense officials that "officials in leading NATO countries have allowed themselves to make aggressive comments about our country, therefore I hereby order the Minister of Defense and the chief of the General Staff to place the Russian Army Deterrence Force on combat alert."

When asked what Putin thought he had achieved in Ukraine so far, Peskov answered, "Well, first of all, not yet. He hasn't achieved yet."

The spokesman claimed that the "special military operation" in Ukraine was "going on strictly in accordance with the plans and the purposes that were established before hand."

He also claimed that Russia has only attacked military targets, despite numerous reports of Russian air strikes against civilian targets sheltering ordinary Ukrainians.